diff --git a/src/api/management/src/request/alerts/templates.rs b/src/api/management/src/request/alerts/templates.rs
index 78faea2e0e..b365958893 100644
--- a/src/api/management/src/request/alerts/templates.rs
+++ b/src/api/management/src/request/alerts/templates.rs
@@ -485,7 +485,11 @@ pub async fn preview_template(
 
     match preview(&req) {
         Ok(resp) => MetaHttpResponse::json(resp),
-        Err(e @ PreviewError::UnknownChannel(_)) | Err(e @ PreviewError::UnknownSeverity(_)) => {
+        Err(e @ PreviewError::UnknownChannel(_))
+        | Err(e @ PreviewError::UnknownSeverity(_))
+        // The draft fails the same validation `save` applies — the client sent
+        // content it could not have saved, so this is a 400 like the others.
+        | Err(e @ PreviewError::InvalidContent(_)) => {
             MetaHttpResponse::bad_request(e.to_string())
         }
         // Unreachable today (the webhook fallback is total), but a render
diff --git a/src/config/src/meta/alerts/content_spec.rs b/src/config/src/meta/alerts/content_spec.rs
index ba24ca3652..1ae10a21b8 100644
--- a/src/config/src/meta/alerts/content_spec.rs
+++ b/src/config/src/meta/alerts/content_spec.rs
@@ -100,10 +100,167 @@ pub struct ChartSpec {
     pub enabled: bool,
 }
 
+/// Schemes an authored link URL may carry.
+///
+/// Mirrors the render layer's allowlist (`alerts::notifications::render::
+/// safe_url`) on purpose, but note which layer actually enforces what:
+///
+/// * **This check is a UX gate, not the security boundary.** It rejects a hostile scheme the author
+///   typed LITERALLY, so they get a clear error at save time instead of a template whose link is
+///   silently neutralized on every send forever after.
+/// * **The render layer is what actually stops delivery.** Link URLs are templates: a scheme that
+///   only materializes after `{variable}` substitution cannot be judged here at all, and `safe_url`
+///   / `dispatchable_url` are what catch it. They also cover every template saved BEFORE this
+///   validation existed.
+///
+/// So a URL passing this function is NOT thereby trusted — see the render
+/// module's docs for the per-medium drop/substitute rules.
+const ALLOWED_LINK_SCHEMES: [&str; 3] = ["http", "https", "mailto"];
+
+/// Reject a link URL whose author-written scheme is not allowlisted.
+///
+/// An allowlist, not a blocklist, because a blocklist fails OPEN: `java\tscript:`,
+/// `\0javascript:`, `java%73cript:` and `vbscript:` all slip past a naive
+/// `starts_with("javascript:")` while a conformant client still dispatches
+/// them. None of them *begin* with an allowed scheme, so an allowlist closes
+/// all of them at once and fails closed on schemes nobody has thought of yet.
+///
+/// A link field holds a URL — so the value must actually LOOK like one. Three
+/// shapes are accepted, and nothing else:
+///
+/// * **Absolute** — `http:`, `https:` or `mailto:` (the scheme allowlist).
+/// * **Root-relative** (`/path`, `?q=1`, `#frag`) — inert, resolves against the deployment's own
+///   host, and an author writing one is doing something legitimate (it renders fine in email).
+/// * **Placeholder-led** (`{alert_url}`, `{alert_url}&tab=logs`, `{scheme}://host`) — link URLs are
+///   TEMPLATES resolved by `substitute_raw` at send time, so there may be no author scheme to judge
+///   yet. The render-time filter catches a hostile substituted value.
+///
+/// A bare word (`foo`, `javascript(0)`, `not a url at all`) or a bare host
+/// (`runbook.example.com/x`) is REJECTED. None can execute anything — a
+/// scheme-less string is just a relative path — but none is a working link
+/// either, and silently accepting one means the author discovers the dead
+/// link when an alert fires instead of when they save.
+fn link_scheme_is_allowed(url: &str) -> bool {
+    let trimmed = url.trim();
+
+    if trimmed.is_empty() {
+        return false;
+    }
+
+    // Whitespace and control characters are never valid inside a URL.
+    if trimmed.chars().any(|c| c.is_whitespace() || c.is_control()) {
+        return false;
+    }
+
+    // A `:` only introduces a scheme when it precedes any path/query/fragment
+    // marker, per RFC 3986 — so `/a:b` is a scheme-less path, not a scheme.
+    let scheme_end = trimmed
+        .find([':', '/', '?', '#'])
+        .filter(|&i| trimmed.as_bytes()[i] == b':');
+
+    let Some(end) = scheme_end else {
+        // No scheme: accept a root-relative reference, or a template whose
+        // scheme only materializes after substitution.
+        return trimmed.starts_with(['/', '?', '#']) || is_variable_led(trimmed);
+    };
+
+    let scheme = &trimmed[..end];
+
+    // A scheme that is ENTIRELY a variable has nothing to judge yet —
+    // `{scheme}://host` is a legitimate template. Deliberately strict:
+    // `{x}javascript:...` also begins with `{`, but the rest of its scheme is
+    // the literal, hostile `javascript`, so it must be rejected.
+    if scheme.starts_with('{') && scheme.ends_with('}') && !scheme[1..].contains('{') {
+        return true;
+    }
+
+    // Schemes are ASCII case-insensitive per RFC 3986.
+    if !ALLOWED_LINK_SCHEMES
+        .iter()
+        .any(|allowed| scheme.eq_ignore_ascii_case(allowed))
+    {
+        return false;
+    }
+
+    // An allowlisted scheme is necessary but NOT sufficient — `http:` and
+    // `https://` carry one and are still not URLs. Delegate the actual
+    // question to a WHATWG-conformant parser rather than hand-rolling it.
+    //
+    // A `{variable}` inside the path/query is fine: it percent-encodes and
+    // still parses, so the substituted value is what ultimately matters.
+    let Ok(parsed) = ::url::Url::parse(trimmed) else {
+        return false;
+    };
+
+    if parsed.scheme().eq_ignore_ascii_case("mailto") {
+        // The parser accepts ANY opaque path after `mailto:`, including an
+        // empty one, so the mailbox shape is checked here: `local@domain`
+        // with a dot in the domain.
+        let addr = parsed.path();
+        let Some((local, domain)) = addr.split_once('@') else {
+            return false;
+        };
+        return !local.is_empty() && domain.contains('.') && !domain.starts_with('.');
+    }
+
+    // http(s): the parser already guarantees a non-empty host (an empty host
+    // is a parse FAILURE for a special scheme). Reject hosts that parse but
+    // can never resolve — `.`, `..`, `-` and friends.
+    match parsed.host_str() {
+        Some(host) => {
+            !host.is_empty()
+                && host.chars().any(|c| c.is_ascii_alphanumeric())
+                && !host.starts_with(['.', '-'])
+                && !host.ends_with(['.', '-'])
+        }
+        None => false,
+    }
+}
+
+/// True when `url` begins with a `{variable}` and the remainder is plausible
+/// URL tail (no whitespace — already checked — and not obvious prose).
+///
+/// `{alert_url}` and `{alert_url}&tab=logs` are legitimate templates whose
+/// real value only exists at send time; `{x} not a url` is not.
+fn is_variable_led(url: &str) -> bool {
+    let Some(rest) = url.strip_prefix('{') else {
+        return false;
+    };
+    let Some(close) = rest.find('}') else {
+        return false;
+    };
+    // A non-empty variable name, and nothing unparseable glued on after it.
+    !rest[..close].is_empty()
+}
+
 impl ContentSpec {
     pub fn parse(body: &str) -> Result<ContentSpec, serde_json::Error> {
         serde_json::from_str(body)
     }
+
+    /// Validate authored content beyond what serde can express.
+    ///
+    /// Returns a human-readable error naming the offending link, so the author
+    /// can fix the template instead of discovering at alert time that a link
+    /// was dropped (#13742).
+    pub fn validate(&self) -> Result<(), String> {
+        for link in &self.links {
+            if !link_scheme_is_allowed(&link.url) {
+                let label = if link.label.is_empty() {
+                    "<unlabeled>"
+                } else {
+                    link.label.as_str()
+                };
+                return Err(format!(
+                    "link '{label}' has an unsupported URL scheme: {:?}. \
+                     Links must use http, https or mailto (a relative path or \
+                     a {{variable}} is also allowed).",
+                    link.url
+                ));
+            }
+        }
+        Ok(())
+    }
 }
 
 #[cfg(test)]
@@ -142,4 +299,131 @@ mod tests {
     fn rejects_non_json() {
         assert!(ContentSpec::parse("Slack payload {alert_name}").is_err());
     }
+
+    /// #13742: a link URL carrying an active-content scheme is rejected AT
+    /// SAVE TIME with a clear error, rather than being stored and silently
+    /// neutralized (or, before the fix, killing the whole notification) on
+    /// every send forever after.
+    #[test]
+    fn rejects_link_urls_with_disallowed_schemes() {
+        for hostile in [
+            "javascript:alert(1)",
+            "JavaScript:alert(1)",   // scheme match is case-insensitive
+            "  javascript:alert(1)", // and ignores surrounding whitespace
+            "java\tscript:alert(1)", // control chars stripped by clients
+            "java\nscript:alert(1)",
+            "\u{0}javascript:alert(1)", // NUL is not Unicode whitespace
+            "java%73cript:alert(1)",    // percent-encoded scheme
+            "vbscript:msgbox(1)",
+            "file:///etc/passwd",
+            "data:text/html,<script>1",
+            // A variable elsewhere in the URL does not excuse a hostile
+            // scheme written literally in scheme position.
+            "{x}javascript:alert(1)",
+            // A link field holds a URL. These are not URLs — they are typos or
+            // garbage, and accepting them means the author only finds out the
+            // link is dead when an alert fires.
+            "javascript(0)",
+            "not a url at all",
+            "foo",
+            "runbook.example.com/x", // bare host: no scheme, ambiguous — require one
+            // An allowlisted scheme with NO HOST. Per the WHATWG URL Standard
+            // an empty host is a parse FAILURE for a special scheme (http/
+            // https), not a warning — these are not URLs.
+            "http:",
+            "http://",
+            "https://",
+            "http:///",
+            "http://?q=1",
+            "http://#frag",
+            "https:// ",
+            // Hosts that parse but cannot resolve to anything real.
+            "https://.",
+            "http://..",
+            "https://-",
+            "http://.:80",
+            // `mailto:` needs a real mailbox. The URL parser accepts ANY
+            // opaque path after the scheme (even empty), so the address shape
+            // has to be checked separately or `mailto:` alone would pass.
+            "mailto:",
+            "mailto:foo", // no @
+            "mailto:@",
+            "mailto:a@",        // no domain
+            "mailto:@b.com",    // no local part
+            "mailto:a b@c.com", // space in address
+            // A variable-led template must still LOOK like a URL once the
+            // variable is peeled off — a bare `{x}` with junk attached is not.
+            "{x} not a url",
+        ] {
+            let body = serde_json::json!({
+                "title": "t",
+                "body": "b",
+                "links": [{"label": "click", "url": hostile}],
+            })
+            .to_string();
+            let spec = ContentSpec::parse(&body).expect("parses as JSON");
+            let err = spec
+                .validate()
+                .expect_err(&format!("accepted hostile url: {hostile:?}"));
+            // The message must name the offending link so the author can fix
+            // it without guessing which of several links is at fault.
+            assert!(
+                err.contains("click"),
+                "error should name the link label, got: {err}"
+            );
+        }
+    }
+
+    /// Guard against over-rejection — legitimate authored URLs must save.
+    ///
+    /// Link URLs are TEMPLATES: `substitute_raw` resolves `{var}` at send
+    /// time, so a URL whose scheme only exists after substitution (or which
+    /// is entirely a placeholder) has no author-written scheme to judge here
+    /// and must be allowed through. Render-time filtering still guards it.
+    #[test]
+    fn accepts_legitimate_and_templated_link_urls() {
+        for ok in [
+            "https://runbook.example/x",
+            "http://runbook.example/x",
+            "mailto:oncall@example.com",
+            "https://runbook.example/{stream_name}", // templated path
+            "{alert_url}",                           // whole URL is a variable
+            "{alert_url}&tab=logs",                  // ...and one with a suffix
+            "{scheme}://host/x",                     // variable IN scheme position
+            "/web/logs?stream=app",                  // relative: inert, valid in email
+            // Positive counterparts to the hostile uppercase/whitespace cases
+            // above: without these, dropping `eq_ignore_ascii_case` or `.trim()`
+            // would still pass every test while silently over-rejecting.
+            "HTTPS://runbook.example/x",
+            "MailTo:oncall@example.com",
+            "  https://runbook.example/x  ",
+            // Real-world absolute URLs must keep working.
+            "https://o2.example:8443/web/logs?a=1#f",
+            "http://localhost:5080/web/logs",
+            "https://user:pass@host.example/x", // userinfo is legal
+            "https://[::1]:8080/x",             // IPv6 literal
+            "https://192.168.1.1/x",            // IPv4 literal
+        ] {
+            let body = serde_json::json!({
+                "title": "t",
+                "body": "b",
+                "links": [{"label": "click", "url": ok}],
+            })
+            .to_string();
+            let spec = ContentSpec::parse(&body).expect("parses as JSON");
+            assert!(
+                spec.validate().is_ok(),
+                "over-rejected legitimate url: {ok:?}"
+            );
+        }
+    }
+
+    /// A spec with no links at all validates — the shipped default content
+    /// template has `links: []`, so this must never start failing or every
+    /// node would fail to seed its templates at startup.
+    #[test]
+    fn accepts_spec_without_links() {
+        let spec = ContentSpec::parse(r#"{"title":"t","body":"b"}"#).unwrap();
+        assert!(spec.validate().is_ok());
+    }
 }
diff --git a/src/core/src/alerts/alert.rs b/src/core/src/alerts/alert.rs
index 31641b8b4b..e6e88a247f 100644
--- a/src/core/src/alerts/alert.rs
+++ b/src/core/src/alerts/alert.rs
@@ -2663,7 +2663,7 @@ async fn send_http_notification(endpoint: &Endpoint, msg: String) -> Result<Stri
         config::metrics::ALERT_CHART_EVENTS_TOTAL
             .with_label_values(&["slack_image_pre_stripped"])
             .inc();
-        msg = stripped;
+        msg = stripped.msg;
     }
 
     let resp = match build_req(msg.clone()).send().await {
@@ -2690,22 +2690,37 @@ async fn send_http_notification(endpoint: &Endpoint, msg: String) -> Result<Stri
             && resp_status == reqwest::StatusCode::BAD_REQUEST
             && (resp_body.contains("invalid_attachments") || resp_body.contains("invalid_blocks"))
             && let Some(stripped) = slack_render::strip_image_blocks(&msg)
-            && let Ok(retry_resp) = build_req(stripped).send().await
+            && let Ok(retry_resp) = build_req(stripped.msg).send().await
             && retry_resp.status().is_success()
         {
-            slack_render::mark_images_undeliverable(now_secs);
             config::metrics::ALERT_CHART_EVENTS_TOTAL
                 .with_label_values(&["slack_image_rejected"])
                 .inc();
-            log::warn!(
-                "[ALERT_CHART] Slack rejected the notification ({resp_body}) because its image \
-                 proxy could not fetch the chart image; delivered without the image. Slack must \
-                 be able to reach {} from the public internet — or set \
-                 ZO_ALERT_CHART_ENABLED=false to stop embedding charts.",
-                config::get_config().common.web_url,
-            );
+            // Removing the image fixed THIS send — but that only says
+            // something about `ZO_WEB_URL`'s reachability when the image we
+            // removed was actually ours. A custom template embedding a
+            // third-party image Slack dislikes must not suppress charts
+            // process-wide for an hour, nor be reported as a `web_url`
+            // problem the operator would then go and "fix" in vain.
+            if stripped.had_web_url_image {
+                slack_render::mark_images_undeliverable(now_secs);
+                log::warn!(
+                    "[ALERT_CHART] Slack rejected the notification ({resp_body}) because its \
+                     image proxy could not fetch the chart image; delivered without the image. \
+                     Slack must be able to reach {} from the public internet — or set \
+                     ZO_ALERT_CHART_ENABLED=false to stop embedding charts.",
+                    config::get_config().common.web_url,
+                );
+            } else {
+                log::warn!(
+                    "[ALERT_CHART] Slack rejected the notification ({resp_body}); it was \
+                     delivered after removing its image block(s). The image did not point at \
+                     this deployment's web_url, so the chart-image suppression was NOT engaged \
+                     — check the image URLs in the destination's template."
+                );
+            }
             return Ok(format!(
-                "sent status: {} (chart image stripped: Slack could not fetch it)",
+                "sent status: {} (image stripped: Slack rejected it)",
                 reqwest::StatusCode::OK,
             ));
         }
diff --git a/src/core/src/alerts/notifications/preview.rs b/src/core/src/alerts/notifications/preview.rs
index f8be38f53c..052d75752b 100644
--- a/src/core/src/alerts/notifications/preview.rs
+++ b/src/core/src/alerts/notifications/preview.rs
@@ -87,6 +87,8 @@ pub enum PreviewError {
     UnknownChannel(String),
     UnknownSeverity(String),
     RenderFailed(String),
+    /// Draft fails the same content validation `templates::save` applies.
+    InvalidContent(String),
 }
 
 impl std::fmt::Display for PreviewError {
@@ -98,6 +100,7 @@ impl std::fmt::Display for PreviewError {
                 "unknown severity: {s} (expected critical, warning, ok, no_data, or single_level)"
             ),
             Self::RenderFailed(e) => write!(f, "preview render failed: {e}"),
+            Self::InvalidContent(e) => write!(f, "{e}"),
         }
     }
 }
@@ -200,6 +203,15 @@ pub fn synthetic_context(level: Option<AlertLevel>) -> NotificationContext {
 pub fn preview(req: &PreviewRequest) -> Result<PreviewResponse, PreviewError> {
     let format = parse_channel(&req.channel)?;
     let level = parse_severity(&req.severity)?;
+
+    // Hold the draft to the same bar `templates::save` applies. Previewing a
+    // spec that cannot be saved would report it as fine and defer the error
+    // to the save click — and `preview_model.links` echoes the raw authored
+    // URL back to the UI, so it must not carry a hostile scheme either.
+    req.definition
+        .validate()
+        .map_err(PreviewError::InvalidContent)?;
+
     let ctx = synthetic_context(level);
 
     let content = resolve_content(&req.definition, &ctx, format.channel_family());
@@ -271,10 +283,34 @@ fn sample_spec() -> ContentSpec {
 
 #[cfg(test)]
 mod tests {
-    use config::meta::alerts::content_spec::{ContentField, SeverityFilter};
+    use config::meta::alerts::content_spec::{ContentField, ContentLink, SeverityFilter};
 
     use super::*;
 
+    /// A draft whose link scheme `save` would reject must be rejected here
+    /// too. Previewing it cleanly and only failing on save teaches the author
+    /// the template is fine when it is not (#13742).
+    #[test]
+    fn preview_rejects_a_draft_the_save_path_would_reject() {
+        let mut spec = sample_spec();
+        spec.links.push(ContentLink {
+            label: "click".into(),
+            url: "javascript:alert(1)".into(),
+            show_when: None,
+        });
+        let req = PreviewRequest {
+            definition: spec,
+            channel: "slack".into(),
+            severity: Some("critical".into()),
+            sample: None,
+        };
+        let err = preview(&req).expect_err("hostile link previewed cleanly");
+        assert!(
+            err.to_string().contains("click"),
+            "error should name the offending link, got: {err}"
+        );
+    }
+
     #[test]
     fn preview_uses_production_renderer() {
         let req = PreviewRequest {
diff --git a/src/core/src/alerts/notifications/render/discord.rs b/src/core/src/alerts/notifications/render/discord.rs
index 39aaff961e..9efaec9b10 100644
--- a/src/core/src/alerts/notifications/render/discord.rs
+++ b/src/core/src/alerts/notifications/render/discord.rs
@@ -26,7 +26,8 @@
 use serde_json::{Value, json};
 
 use super::{
-    DEFAULT_LINK_LABEL, clamp, markdown::escape_discord_markdown, safe_url, severity_color,
+    DEFAULT_LINK_LABEL, clamp, dispatchable_url, markdown::escape_discord_markdown, safe_url,
+    severity_color,
 };
 use crate::alerts::notifications::{NotificationContext, resolve::RenderedContent};
 
@@ -95,7 +96,16 @@ pub fn render_discord(c: &RenderedContent, ctx: &NotificationContext) -> Value {
     // link, not a button list. Any further author-added links have no embed
     // slot to render into and are appended to the description as markdown
     // links instead.
-    let embed_url = c.links.first().map(|(_, url)| safe_url(url).to_string());
+    // Discord validates `embed.url` and rejects the message when it is not an
+    // absolute http(s) URL, so an undispatchable first link yields NO embed
+    // url rather than an invalid one (#13742's failure class). The markdown
+    // links appended to the description below are inert TEXT, so they keep
+    // `safe_url`'s neutralize-in-place behaviour instead.
+    let embed_url = c
+        .links
+        .first()
+        .and_then(|(_, url)| dispatchable_url(url))
+        .map(str::to_string);
     let extra_links = if c.links.is_empty() {
         &c.links[..]
     } else {
diff --git a/src/core/src/alerts/notifications/render/mod.rs b/src/core/src/alerts/notifications/render/mod.rs
index 2f34a4e3d1..83da71a9e9 100644
--- a/src/core/src/alerts/notifications/render/mod.rs
+++ b/src/core/src/alerts/notifications/render/mod.rs
@@ -33,14 +33,35 @@
 //! | HTML email | HTML entity-encoded; raw `<script>` never emitted |
 //! | Webhook / all JSON | `serde_json` serialization |
 //!
-//! One defense IS global: [`safe_url`] restricts link URLs to an ALLOWLIST of
-//! schemes (`http`, `https`, `mailto`, plus scheme-less relative URLs) in every
-//! renderer that emits a link. Link URLs are author-supplied templates that
-//! undergo variable substitution, so they are not trusted constants. An
+//! Link URLs get a scheme ALLOWLIST ([`safe_url`]: `http`, `https`, `mailto`,
+//! plus scheme-less relative URLs). Link URLs are author-supplied templates
+//! that undergo variable substitution, so they are not trusted constants. An
 //! allowlist rather than a blocklist because it fails closed: control
 //! characters, NUL prefixes and percent-encoding all defeat a naive
 //! `javascript:`/`data:` blocklist while clients still dispatch the URL.
 //!
+//! Being SAFE is not the same as being DELIVERABLE, and URLs need both.
+//! `safe_url` neutralizes a hostile scheme by substituting [`BLOCKED_URL`]
+//! ("#") — valid and inert in HTML email, but Slack, Teams, Discord and
+//! PagerDuty validate action URLs server-side and reject the ENTIRE payload
+//! when one is not an absolute `http(s)` URL. Substituting there cost the
+//! alert its delivery (`400 invalid_attachments`, #13742). So those renderers
+//! pass links through [`dispatchable_url`] and DROP what they cannot send,
+//! while the forgiving media keep substituting.
+//!
+//! This is NOT uniform across renderers — choose by medium, and check this
+//! table before adding a renderer or a new URL sink:
+//!
+//! | renderer | link handling |
+//! |---|---|
+//! | Slack buttons, Teams actions, Discord `embed.url`, PagerDuty `href` | [`dispatchable_url`] → drop |
+//! | HTML email, email plaintext, SNS plaintext, Discord description | [`safe_url`] → substitute `#` |
+//! | Webhook envelope | UNFILTERED — a versioned machine contract; see [`webhook`] |
+//!
+//! The webhook envelope is the one deliberate exemption: it is parsed by other
+//! systems, so rewriting a URL to `#` would corrupt the data it promises to
+//! carry. Its consumers must treat `links[].url` as untrusted.
+//!
 //! Pure functions — no I/O, no async.
 
 pub mod discord;
@@ -213,6 +234,75 @@ pub(crate) fn safe_url(url: &str) -> &str {
     }
 }
 
+/// Schemes a transport will accept as an ACTION target (button, card action).
+const DISPATCHABLE_URL_SCHEMES: [&str; 2] = ["http", "https"];
+
+/// Restrict a link URL to one that a strict transport will actually deliver.
+///
+/// [`safe_url`] answers "is this URL inert?"; this answers the different
+/// question "will the transport accept it?" — and the two are NOT the same.
+/// Slack, Teams and Discord validate every action URL server-side and require
+/// an ABSOLUTE `http(s)` URL. Anything else makes them reject the ENTIRE
+/// payload, so a link that cannot be dispatched must be DROPPED by the caller,
+/// never emitted.
+///
+/// Returns `None` for every URL that is safe but undeliverable:
+///
+/// * [`BLOCKED_URL`] — what `safe_url` substitutes for a hostile scheme. Emitting it as a button
+///   URL is what lost the alert in #13742.
+/// * empty / whitespace-only — an unset `ZO_WEB_URL` produces exactly this.
+/// * relative (`/path`, `?q=1`, `#frag`) — legitimate in email, meaningless to Slack, which has no
+///   base URL to resolve against. An empty `ZO_WEB_URL` reaches here too.
+/// * `mailto:` — allowlisted by `safe_url` and correct in an email body, but not a valid button
+///   target.
+/// * scheme-only / opaque / authority-less http(s) (`http:`, `https://`,
+///   `http:javascript:alert(1)`) — an allowlisted scheme alone is NOT enough; Slack needs a host.
+/// * anything containing a raw space or control character, which substitution can introduce.
+///
+/// Callers that render into a forgiving medium (HTML email, plain text) must
+/// keep using [`safe_url`]: there, `href="#"` is valid, inert, and preserves
+/// the visible signal that a link was neutralized.
+pub(crate) fn dispatchable_url(url: &str) -> Option<&str> {
+    let trimmed = safe_url(url).trim();
+
+    // A raw space or control character breaks the transport even when the
+    // scheme and host are fine, and substitution can introduce either.
+    if trimmed
+        .chars()
+        .any(|c| c == ' ' || c.is_control() || c.is_whitespace())
+    {
+        return None;
+    }
+
+    // `safe_url` passes relative URLs through by design; they cannot be
+    // resolved by a transport that has no base URL, so they stop here.
+    let scheme_end = trimmed
+        .find([':', '/', '?', '#'])
+        .filter(|&i| trimmed.as_bytes()[i] == b':')?;
+
+    // Schemes are ASCII case-insensitive per RFC 3986.
+    let scheme = &trimmed[..scheme_end];
+    if !DISPATCHABLE_URL_SCHEMES
+        .iter()
+        .any(|allowed| scheme.eq_ignore_ascii_case(allowed))
+    {
+        return None;
+    }
+
+    // An allowlisted scheme is NOT sufficient. `http:javascript:alert(1)` and
+    // `https://` are both valid RFC 3986 http(s) URLs — the first is OPAQUE
+    // (no authority), the second has an empty one — and Slack rejects both
+    // with the very `400 invalid_attachments` this function exists to
+    // prevent. Require a non-empty authority.
+    let authority = trimmed[scheme_end + 1..].strip_prefix("//")?;
+    let authority_end = authority.find(['/', '?', '#']).unwrap_or(authority.len());
+    if authority[..authority_end].is_empty() {
+        return None;
+    }
+
+    Some(trimmed)
+}
+
 /// Render `content` for `format`.
 pub fn render(
     format: ChannelFormat,
@@ -834,6 +924,16 @@ mod tests {
     /// filtering in one renderer only would invite the reader to assume it is
     /// global when it is not. Every renderer that emits a link is asserted
     /// here so the guarantee cannot silently become partial again.
+    ///
+    /// Two different NEUTRALIZATIONS, by medium (#13742):
+    ///
+    /// * Strict transports (Slack, Teams, Discord) validate action URLs and reject the whole
+    ///   payload if one is invalid, so the hostile link is DROPPED — emitting the `BLOCKED_URL`
+    ///   placeholder there cost the alert its delivery.
+    /// * Forgiving media (HTML email, plain text) SUBSTITUTE the placeholder: `href="#"` is valid
+    ///   and inert, and keeping the row preserves the visible signal that a link was neutralized.
+    ///
+    /// Either way the hostile URL never reaches the recipient.
     #[test]
     fn all_renderers_drop_hostile_url_schemes() {
         for hostile in [
@@ -851,26 +951,59 @@ mod tests {
             "file:///etc/passwd",
         ] {
             let mut c = hostile_content();
-            c.links = vec![("evil".into(), hostile.into())];
+            // A legitimate link alongside the hostile one: without it the
+            // "dropped" assertions below could pass vacuously on a renderer
+            // that emitted no actions at all for an unrelated reason.
+            c.links = vec![
+                ("evil".into(), hostile.into()),
+                ("Runbook".into(), "https://rb.example/x".into()),
+            ];
+            let survivor = "https://rb.example/x";
 
+            // Strict transports: the hostile link is gone, the good one stays.
             let slack = slack::render_slack(&c, &fixture_ctx());
+            let elements = &slack["attachments"][1]["blocks"][0]["elements"];
             assert_eq!(
-                slack["attachments"][1]["blocks"][0]["elements"][0]["url"], BLOCKED_URL,
+                elements.as_array().map(Vec::len),
+                Some(1),
                 "slack leaked {hostile}"
             );
+            assert_eq!(elements[0]["url"], survivor, "slack dropped the wrong link");
 
             let card = teams::render_teams_adaptive_card(&c, &fixture_ctx());
+            let actions = &card["attachments"][0]["content"]["actions"];
             assert_eq!(
-                card["attachments"][0]["content"]["actions"][0]["url"], BLOCKED_URL,
+                actions.as_array().map(Vec::len),
+                Some(1),
                 "adaptive card leaked {hostile}"
             );
+            assert_eq!(
+                actions[0]["url"], survivor,
+                "adaptive card dropped the wrong link"
+            );
 
             let msg = teams::render_teams_message_card(&c);
+            let potential = &msg["potentialAction"];
             assert_eq!(
-                msg["potentialAction"][0]["targets"][0]["uri"], BLOCKED_URL,
+                potential.as_array().map(Vec::len),
+                Some(1),
                 "message card leaked {hostile}"
             );
+            assert_eq!(
+                potential[0]["targets"][0]["uri"], survivor,
+                "message card dropped the wrong link"
+            );
 
+            // PagerDuty validates `links[].href` too.
+            let pd = pagerduty::render_pagerduty(&c, &fixture_ctx());
+            let pd_links = pd["links"].as_array().expect("pagerduty links");
+            assert_eq!(pd_links.len(), 1, "pagerduty leaked {hostile}");
+            assert_eq!(
+                pd_links[0]["href"], survivor,
+                "pagerduty dropped the wrong link"
+            );
+
+            // Forgiving media: the row survives with the placeholder.
             let (_, html, text) = email::render_email(&c, &fixture_ctx());
             // Assert the placeholder positively: a `!contains` alone would
             // pass vacuously if escaping merely reshaped the hostile string.
@@ -882,6 +1015,14 @@ mod tests {
                 text.contains(&format!("evil: {BLOCKED_URL}")),
                 "email text did not block {hostile}"
             );
+
+            // SNS fans out to email/SMS clients that linkify bare URLs, so
+            // its plaintext gets the same substitution as email's.
+            let (_, sns_text) = sns::render_sns(&c);
+            assert!(
+                sns_text.contains(&format!("evil: {BLOCKED_URL}")),
+                "sns did not block {hostile}: {sns_text}"
+            );
         }
     }
 
@@ -938,6 +1079,179 @@ mod tests {
         }
     }
 
+    /// A URL that is SAFE is not automatically DISPATCHABLE.
+    ///
+    /// Regression test for #13742: `safe_url` correctly rewrote
+    /// `javascript:alert(1)` to `BLOCKED_URL` ("#"), the renderer put "#" in a
+    /// Slack button's `url`, and Slack rejected the WHOLE message with
+    /// `400 invalid_attachments` — the alert was lost outright. Slack, Teams
+    /// and Discord validate action URLs server-side and require an absolute
+    /// `http(s)` URL, so every value that is inert-but-relative must be
+    /// reported as undispatchable so the renderer can DROP the link rather
+    /// than emit a payload the transport will reject.
+    #[test]
+    fn dispatchable_url_rejects_safe_but_undeliverable_urls() {
+        for undeliverable in [
+            BLOCKED_URL,      // what safe_url substitutes for a hostile scheme
+            "",               // unset ZO_WEB_URL yields an empty alert_url
+            "   ",            // ...and a whitespace-only one
+            "/web/logs?a=1",  // empty ZO_WEB_URL leaves a root-relative path
+            "?query=1",       // query-only relative URL
+            "#anchor",        // fragment-only relative URL
+            "mailto:a@b.com", // safe + useful in email, invalid as a button URL
+            // An allowlisted scheme is NOT sufficient: Slack needs an
+            // authority too. These are OPAQUE http(s) URLs — valid per
+            // RFC 3986, rejected by Slack, and the same lost-alert bug as
+            // #13742 if they are ever emitted.
+            "http:javascript:alert(1)",
+            "https:alert(1)",
+            "http:",
+            "https://",
+            "https:///path", // authority present but empty
+            // Raw control characters and spaces break the transport even
+            // when the scheme and host are fine.
+            "https://x/ y",
+            "https://x\ny",
+            "https://x\ty",
+            "http://ex.com\u{0}",
+        ] {
+            assert_eq!(
+                dispatchable_url(undeliverable),
+                None,
+                "would be sent to a strict transport: {undeliverable:?}"
+            );
+        }
+
+        // Absolute http(s) URLs remain dispatchable, hostile path notwithstanding.
+        for ok in [
+            "https://o2.example/short/abc",
+            "http://o2.example/web/logs",
+            "  https://o2.example/x  ", // trimmed, not rejected
+            "HTTPS://o2.example/x",     // scheme match is case-insensitive
+        ] {
+            assert_eq!(
+                dispatchable_url(ok),
+                Some(ok.trim()),
+                "over-blocked: {ok:?}"
+            );
+        }
+    }
+
+    /// #13742: a hostile link URL must never cost the alert its delivery.
+    ///
+    /// The blocked link is DROPPED from the action list; the message itself —
+    /// title, body, fields and the legitimate "View in OpenObserve" link —
+    /// still renders and still sends.
+    #[test]
+    fn hostile_link_is_dropped_not_emitted_as_blocked_url() {
+        let mut c = hostile_content();
+        c.links = vec![
+            ("click".into(), "javascript:alert(1)".into()),
+            ("Runbook".into(), "https://rb.example/x".into()),
+            ("".into(), "https://o2.example/short/abc".into()),
+        ];
+
+        let slack = slack::render_slack(&c, &fixture_ctx());
+        let elements = slack["attachments"][1]["blocks"][0]["elements"]
+            .as_array()
+            .expect("slack actions block");
+        // The hostile link is gone; the two legitimate ones survive.
+        assert_eq!(elements.len(), 2, "slack elements: {elements:#?}");
+        for el in elements {
+            let url = el["url"].as_str().expect("button url");
+            assert!(
+                url.starts_with("https://"),
+                "slack emitted a non-dispatchable button url: {url:?}"
+            );
+        }
+
+        let card = teams::render_teams_adaptive_card(&c, &fixture_ctx());
+        let actions = card["attachments"][0]["content"]["actions"]
+            .as_array()
+            .expect("adaptive card actions");
+        assert_eq!(actions.len(), 2, "adaptive card actions: {actions:#?}");
+        for a in actions {
+            let url = a["url"].as_str().expect("action url");
+            assert!(
+                url.starts_with("https://"),
+                "adaptive card emitted a non-dispatchable action url: {url:?}"
+            );
+        }
+
+        let msg = teams::render_teams_message_card(&c);
+        let potential = msg["potentialAction"]
+            .as_array()
+            .expect("message card actions");
+        assert_eq!(potential.len(), 2, "message card actions: {potential:#?}");
+        for a in potential {
+            let uri = a["targets"][0]["uri"].as_str().expect("target uri");
+            assert!(
+                uri.starts_with("https://"),
+                "message card emitted a non-dispatchable uri: {uri:?}"
+            );
+        }
+    }
+
+    /// #13742, config-driven path: an EMPTY `ZO_WEB_URL` makes `alert_url` a
+    /// root-relative path, which reaches the same strict transports through
+    /// the always-appended "View in OpenObserve" link — breaking deployments
+    /// that never authored a hostile template. The action block must not be
+    /// emitted with an undispatchable URL, and when no link survives, no
+    /// empty `actions` block may be emitted either (Slack rejects that too).
+    #[test]
+    fn relative_alert_url_does_not_produce_an_invalid_action_block() {
+        let mut ctx = fixture_ctx();
+        ctx.alert_url = "/web/logs?stream=app&org_identifier=default".into();
+        let mut c = hostile_content();
+        c.links = vec![("".into(), ctx.alert_url.clone())];
+
+        let slack = slack::render_slack(&c, &ctx);
+        // Only the content attachment remains: no buttons, no chart.
+        for att in slack["attachments"].as_array().expect("attachments") {
+            for block in att["blocks"].as_array().expect("blocks") {
+                assert_ne!(
+                    block["type"], "actions",
+                    "slack emitted an actions block built from a relative url: {slack:#?}"
+                );
+            }
+        }
+
+        let card = teams::render_teams_adaptive_card(&c, &ctx);
+        assert!(
+            card["attachments"][0]["content"]["actions"]
+                .as_array()
+                .is_none_or(|a| a.is_empty()),
+            "adaptive card kept a relative action url: {card:#?}"
+        );
+
+        let msg = teams::render_teams_message_card(&c);
+        assert!(
+            msg["potentialAction"]
+                .as_array()
+                .is_none_or(|a| a.is_empty()),
+            "message card kept a relative action uri: {msg:#?}"
+        );
+    }
+
+    /// Email is the deliberate counter-case: `href="#"` is valid, inert HTML,
+    /// so email must keep BLOCKING (substituting) rather than DROPPING —
+    /// the reader still sees the link's label and that it was neutralized.
+    #[test]
+    fn email_still_substitutes_blocked_url_rather_than_dropping() {
+        let mut c = hostile_content();
+        c.links = vec![("evil".into(), "javascript:alert(1)".into())];
+
+        let (_, html, text) = email::render_email(&c, &fixture_ctx());
+        assert!(
+            html.contains(&format!(r#"href="{BLOCKED_URL}""#)),
+            "email html should neutralize, not drop"
+        );
+        assert!(
+            text.contains(&format!("evil: {BLOCKED_URL}")),
+            "email text should neutralize, not drop"
+        );
+    }
+
     /// `row_lines` takes precedence over `rows` in EVERY renderer, not just
     /// Slack (which `row_lines_take_precedence_over_rows` already pins).
     #[test]
diff --git a/src/core/src/alerts/notifications/render/pagerduty.rs b/src/core/src/alerts/notifications/render/pagerduty.rs
index 515cb6a73d..d85a937e18 100644
--- a/src/core/src/alerts/notifications/render/pagerduty.rs
+++ b/src/core/src/alerts/notifications/render/pagerduty.rs
@@ -51,16 +51,20 @@ pub fn render_pagerduty(c: &RenderedContent, ctx: &NotificationContext) -> Value
     }
     custom_details.insert("body".to_string(), Value::String(c.body_markdown.clone()));
 
+    // PagerDuty validates `links[].href` server-side and 400s the whole event
+    // on a malformed one — the same lost-alert failure as #13742 on Slack, so
+    // an undispatchable link is dropped rather than emitted.
     let links: Vec<Value> = c
         .links
         .iter()
+        .filter_map(|(label, url)| super::dispatchable_url(url).map(|url| (label, url)))
         .map(|(label, url)| {
             let text = if label.is_empty() {
                 super::DEFAULT_LINK_LABEL
             } else {
                 label.as_str()
             };
-            json!({"href": super::safe_url(url), "text": text})
+            json!({"href": url, "text": text})
         })
         .collect();
 
diff --git a/src/core/src/alerts/notifications/render/slack.rs b/src/core/src/alerts/notifications/render/slack.rs
index 5893ef6fa2..1b860f729d 100644
--- a/src/core/src/alerts/notifications/render/slack.rs
+++ b/src/core/src/alerts/notifications/render/slack.rs
@@ -18,9 +18,9 @@
 use serde_json::{Value, json};
 
 use super::{
-    DEFAULT_LINK_LABEL, clamp,
+    DEFAULT_LINK_LABEL, clamp, dispatchable_url,
     markdown::{escape_mrkdwn, guard_leading_blockquote, markdown_to_mrkdwn},
-    safe_url, severity_color,
+    severity_color,
 };
 use crate::alerts::notifications::{NotificationContext, resolve::RenderedContent};
 
@@ -39,16 +39,13 @@ pub fn render_slack(c: &RenderedContent, ctx: &NotificationContext) -> Value {
     // Datadog-style clickable title: a bold mrkdwn link section that opens
     // the alert (user-picked over the plain header in a live A/B on a real
     // channel). mrkdwn link syntax breaks on `|` (terminates the label) and
-    // `>` (terminates the link), so a title containing either — and a
-    // missing/blocked alert URL — falls back to the plain `header` block.
-    // The label is escape_mrkdwn'd (entity-encoding `&`/`<`/`>`); the URL is
-    // scheme-checked via `safe_url`.
-    let title_url = safe_url(&ctx.alert_url);
-    if !title_url.is_empty()
-        && !title_url.contains(['|', '>', '<'])
-        && !c.title.contains('|')
-        && title_url != super::BLOCKED_URL
-    {
+    // `>` (terminates the link), so a title containing either — and an
+    // undispatchable alert URL — falls back to the plain `header` block.
+    // The label is escape_mrkdwn'd (entity-encoding `&`/`<`/`>`); the URL must
+    // be an absolute http(s) one (`dispatchable_url`), which also rules out the
+    // blocked placeholder, an empty `ZO_WEB_URL` and relative paths.
+    let title_url = dispatchable_url(&ctx.alert_url).unwrap_or_default();
+    if !title_url.is_empty() && !title_url.contains(['|', '>', '<']) && !c.title.contains('|') {
         blocks.push(json!({
             "type": "section",
             "text": {"type": "mrkdwn", "text": format!(
@@ -133,15 +130,26 @@ pub fn render_slack(c: &RenderedContent, ctx: &NotificationContext) -> Value {
     // user-picked "full stripe" layout).
     let mut tail_blocks: Vec<Value> = Vec::new();
 
-    if !c.links.is_empty() {
+    // Slack validates every button `url` server-side and rejects the WHOLE
+    // message with `400 invalid_attachments` if one is not an absolute
+    // http(s) URL — losing the alert entirely (#13742). A link that cannot be
+    // dispatched is therefore DROPPED here rather than emitted: the alert is
+    // worth more than the button. This filter runs BEFORE the 5-element cap
+    // so a dropped link frees its slot for a deliverable one.
+    let deliverable: Vec<(&String, &str)> = c
+        .links
+        .iter()
+        .filter_map(|(label, url)| dispatchable_url(url).map(|url| (label, url)))
+        .collect();
+
+    if !deliverable.is_empty() {
         // The appended "View in OpenObserve" link (empty label, always last —
         // resolve.rs) is the notification's primary action: it must survive
         // the 5-element cap, so author links only fill the remaining slots.
-        let default_count = c.links.iter().filter(|(l, _)| l.is_empty()).count();
+        let default_count = deliverable.iter().filter(|(l, _)| l.is_empty()).count();
         let author_cap = MAX_ACTION_ELEMENTS.saturating_sub(default_count.min(MAX_ACTION_ELEMENTS));
         let mut authored_kept = 0usize;
-        let elements: Vec<Value> = c
-            .links
+        let elements: Vec<Value> = deliverable
             .iter()
             .filter(|(label, _)| {
                 if label.is_empty() {
@@ -162,7 +170,7 @@ pub fn render_slack(c: &RenderedContent, ctx: &NotificationContext) -> Value {
                 let mut button = json!({
                     "type": "button",
                     "text": {"type": "plain_text", "text": clamp(label, 75)},
-                    "url": safe_url(url),
+                    "url": url,
                 });
                 // The default "View in OpenObserve" link is the notification's
                 // primary action — Slack's "primary" button style renders it
@@ -240,17 +248,76 @@ pub fn images_undeliverable(now_secs: u64) -> bool {
     at != 0 && now_secs.saturating_sub(at) < IMAGES_RETRY_SECS
 }
 
+/// Outcome of stripping a payload's image blocks.
+pub struct StrippedPayload {
+    /// The payload with every `image` block removed.
+    pub msg: String,
+    /// Whether any stripped image pointed at OUR `web_url`.
+    ///
+    /// Only such an image is evidence about *this deployment's* reachability
+    /// from Slack's proxy. A custom template embedding a third-party image
+    /// that Slack rejects says nothing about `ZO_WEB_URL`, so it must not
+    /// trip the process-wide suppression flag or claim that diagnosis in the
+    /// log — see `mark_images_undeliverable`.
+    pub had_web_url_image: bool,
+}
+
+/// True when `url` sits under `base` — matching at a component boundary, not
+/// as a bare prefix.
+///
+/// `starts_with` alone would treat `https://o2.example.attacker.test/x` as
+/// living under `https://o2.example`, mis-attributing someone else's image to
+/// this deployment. The character after the base must therefore end the
+/// authority (`/`, `?`, `#`) or the URL must be exactly the base.
+///
+/// Scheme and host are ASCII case-insensitive (RFC 3986), so the comparison is
+/// too — otherwise `ZO_WEB_URL=https://O2.example` would never match the chart
+/// URL and image suppression would silently never engage.
+fn url_has_base(url: &str, base: &str) -> bool {
+    let base = base.trim_end_matches('/');
+    // `get` rather than slicing: a multi-byte character straddling
+    // `base.len()` would panic on a raw index.
+    let Some(head) = url.get(..base.len()) else {
+        return false;
+    };
+    // Only the scheme+authority is case-insensitive; the path is not. `base`
+    // is a bare origin in practice, so comparing its whole length is correct.
+    if !head.eq_ignore_ascii_case(base) {
+        return false;
+    }
+    let rest = &url[base.len()..];
+    rest.is_empty() || rest.starts_with(['/', '?', '#'])
+}
+
 /// Remove every `image` block from a Slack payload — top-level `blocks` and
 /// each attachment's `blocks` — dropping any attachment left with no blocks
 /// (an empty-`blocks` attachment renders a bare color stripe fragment).
 /// Returns `None` when the payload isn't JSON or has no image block, i.e.
 /// when stripping cannot change the outcome.
-pub fn strip_image_blocks(msg: &str) -> Option<String> {
+pub fn strip_image_blocks(msg: &str) -> Option<StrippedPayload> {
+    strip_image_blocks_with_base(msg, &config::get_config().common.web_url)
+}
+
+/// [`strip_image_blocks`] with the `web_url` injected, so tests need no global
+/// config. `web_url_base` empty ⇒ no image can be attributed to us.
+pub fn strip_image_blocks_with_base(msg: &str, web_url_base: &str) -> Option<StrippedPayload> {
     let mut v: Value = serde_json::from_str(msg).ok()?;
     let mut removed = false;
+    let mut had_web_url_image = false;
     let mut strip = |blocks: &mut Vec<Value>| {
         let before = blocks.len();
-        blocks.retain(|b| b.get("type").and_then(Value::as_str) != Some("image"));
+        blocks.retain(|b| {
+            let is_image = b.get("type").and_then(Value::as_str) == Some("image");
+            if is_image
+                && !web_url_base.is_empty()
+                && b.get("image_url")
+                    .and_then(Value::as_str)
+                    .is_some_and(|u| url_has_base(u, web_url_base))
+            {
+                had_web_url_image = true;
+            }
+            !is_image
+        });
         removed |= blocks.len() != before;
     };
     if let Some(blocks) = v.get_mut("blocks").and_then(Value::as_array_mut) {
@@ -269,20 +336,29 @@ pub fn strip_image_blocks(msg: &str) -> Option<String> {
                 .is_none_or(|b| !b.is_empty())
         });
     }
-    removed.then(|| v.to_string())
+    removed.then(|| StrippedPayload {
+        msg: v.to_string(),
+        had_web_url_image,
+    })
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    const BASE: &str = "https://o2.example";
+
+    fn strip(msg: &str) -> Option<StrippedPayload> {
+        strip_image_blocks_with_base(msg, BASE)
+    }
+
     #[test]
     fn strip_removes_image_blocks_but_keeps_attachments_with_content() {
         let msg = r##"{"attachments":[
             {"color":"#c00","blocks":[{"type":"section"}]},
             {"color":"#c00","blocks":[{"type":"actions"},{"type":"image","image_url":"http://x/c.png","alt_text":"t"}]}
         ]}"##;
-        let out = strip_image_blocks(msg).unwrap();
+        let out = strip(msg).unwrap().msg;
         let v: Value = serde_json::from_str(&out).unwrap();
         let attachments = v["attachments"].as_array().unwrap();
         assert_eq!(attachments.len(), 2, "actions attachment must survive");
@@ -296,7 +372,7 @@ mod tests {
             {"color":"#c00","blocks":[{"type":"section"}]},
             {"color":"#c00","blocks":[{"type":"image","image_url":"http://x/c.png","alt_text":"t"}]}
         ]}"##;
-        let v: Value = serde_json::from_str(&strip_image_blocks(msg).unwrap()).unwrap();
+        let v: Value = serde_json::from_str(&strip(msg).unwrap().msg).unwrap();
         assert_eq!(v["attachments"].as_array().unwrap().len(), 1);
     }
 
@@ -304,17 +380,66 @@ mod tests {
     fn strip_handles_top_level_blocks_from_custom_templates() {
         let msg =
             r#"{"blocks":[{"type":"section"},{"type":"image","image_url":"u","alt_text":"t"}]}"#;
-        let v: Value = serde_json::from_str(&strip_image_blocks(msg).unwrap()).unwrap();
+        let v: Value = serde_json::from_str(&strip(msg).unwrap().msg).unwrap();
         assert_eq!(v["blocks"].as_array().unwrap().len(), 1);
     }
 
     #[test]
     fn strip_returns_none_when_nothing_to_do() {
-        assert!(
-            strip_image_blocks(r#"{"attachments":[{"blocks":[{"type":"section"}]}]}"#).is_none()
+        assert!(strip(r#"{"attachments":[{"blocks":[{"type":"section"}]}]}"#).is_none());
+        assert!(strip("not json").is_none());
+        assert!(strip(r#"{"text":"plain"}"#).is_none());
+    }
+
+    /// The process-wide chart suppression may only engage on evidence about
+    /// THIS deployment: an image we generated, pointing at our `web_url`.
+    ///
+    /// Attributing a third-party image's rejection to `ZO_WEB_URL` would both
+    /// suppress legitimate charts for an hour across every alert and send the
+    /// operator to "fix" a `web_url` that was never broken.
+    #[test]
+    fn only_our_own_image_url_is_evidence_about_web_url_reachability() {
+        // Our chart render URL: attributable.
+        let ours = format!(
+            r#"{{"attachments":[{{"blocks":[{{"type":"image","image_url":"{BASE}/api/v2/default/alerts/charts/render?d=x","alt_text":"c"}}]}}]}}"#
         );
-        assert!(strip_image_blocks("not json").is_none());
-        assert!(strip_image_blocks(r#"{"text":"plain"}"#).is_none());
+        assert!(strip(&ours).unwrap().had_web_url_image);
+
+        // A custom template's third-party image: NOT attributable.
+        let theirs = r#"{"attachments":[{"blocks":[{"type":"image","image_url":"https://cdn.example/logo.png","alt_text":"c"}]}]}"#;
+        assert!(!strip(theirs).unwrap().had_web_url_image);
+
+        // A lookalike host must not be mistaken for ours.
+        let lookalike = r#"{"attachments":[{"blocks":[{"type":"image","image_url":"https://o2.example.attacker.test/x.png","alt_text":"c"}]}]}"#;
+        assert!(
+            !strip(lookalike).unwrap().had_web_url_image,
+            "prefix match must not be fooled by a lookalike host"
+        );
+
+        // Mixed payload: one of ours among others still counts as evidence.
+        let mixed = format!(
+            r#"{{"blocks":[{{"type":"image","image_url":"https://cdn.example/a.png","alt_text":"a"}},{{"type":"image","image_url":"{BASE}/api/v2/x","alt_text":"b"}}]}}"#
+        );
+        assert!(strip(&mixed).unwrap().had_web_url_image);
+
+        // An unset web_url can attribute nothing to us.
+        let unset = strip_image_blocks_with_base(&ours, "").unwrap();
+        assert!(!unset.had_web_url_image);
+
+        // Scheme and host are case-insensitive (RFC 3986): a `ZO_WEB_URL`
+        // written with different casing must still match, or suppression
+        // would silently never engage on that deployment.
+        let cased = strip_image_blocks_with_base(&ours, "HTTPS://O2.example").unwrap();
+        assert!(cased.had_web_url_image, "host comparison must ignore case");
+
+        // A trailing slash on the configured base must not break matching.
+        let slashed = strip_image_blocks_with_base(&ours, &format!("{BASE}/")).unwrap();
+        assert!(slashed.had_web_url_image);
+
+        // A multi-byte character where the base boundary falls must not panic.
+        let multibyte =
+            r#"{"blocks":[{"type":"image","image_url":"https://o2.exampleé/x","alt_text":"c"}]}"#;
+        assert!(!strip(multibyte).unwrap().had_web_url_image);
     }
 
     #[test]
diff --git a/src/core/src/alerts/notifications/render/sns.rs b/src/core/src/alerts/notifications/render/sns.rs
index fa1456a30f..2349368691 100644
--- a/src/core/src/alerts/notifications/render/sns.rs
+++ b/src/core/src/alerts/notifications/render/sns.rs
@@ -48,8 +48,13 @@ pub fn render_sns(c: &RenderedContent) -> (String, String) {
             c.links
                 .iter()
                 .map(|(label, url)| {
+                    // Same scheme filter as email's plaintext part: an SNS
+                    // subscription fans out to email/SMS clients that
+                    // linkify bare URLs, so a hostile scheme must not
+                    // survive into the text a human taps.
+                    let url = super::safe_url(url);
                     if label.is_empty() {
-                        url.clone()
+                        url.to_string()
                     } else {
                         format!("{label}: {url}")
                     }
diff --git a/src/core/src/alerts/notifications/render/teams.rs b/src/core/src/alerts/notifications/render/teams.rs
index 59b6dcad53..a32290b1fd 100644
--- a/src/core/src/alerts/notifications/render/teams.rs
+++ b/src/core/src/alerts/notifications/render/teams.rs
@@ -20,9 +20,9 @@ use config::meta::alerts::level::AlertLevel;
 use serde_json::{Value, json};
 
 use super::{
-    DEFAULT_LINK_LABEL, clamp,
+    DEFAULT_LINK_LABEL, clamp, dispatchable_url,
     markdown::{escape_html, markdown_to_plaintext},
-    safe_url, severity_color,
+    severity_color,
 };
 use crate::alerts::notifications::{NotificationContext, resolve::RenderedContent};
 
@@ -116,15 +116,19 @@ pub fn render_teams_adaptive_card(c: &RenderedContent, ctx: &NotificationContext
         }));
     }
 
+    // `Action.OpenUrl` requires an absolute http(s) URL: a relative one or the
+    // blocked placeholder makes Teams reject the card (the same failure class
+    // as #13742 on Slack), so an undispatchable link is dropped, not emitted.
     let actions: Vec<Value> = c
         .links
         .iter()
+        .filter_map(|(label, url)| dispatchable_url(url).map(|url| (label, url)))
         .map(|(label, url)| {
             let is_default_link = label.is_empty();
             let mut action = json!({
                 "type": "Action.OpenUrl",
                 "title": if is_default_link { DEFAULT_LINK_LABEL.to_string() } else { card_text(label) },
-                "url": safe_url(url),
+                "url": url,
             });
             // Mirrors the Slack "primary"-style fix: the default
             // "View in OpenObserve" action is the card's primary CTA and
@@ -207,14 +211,18 @@ pub fn render_teams_message_card(c: &RenderedContent) -> Value {
         );
     }
 
+    // `OpenUri` targets must be absolute http(s) URIs — the O365 connector
+    // rejects anything else, so undispatchable links are dropped (see the
+    // Adaptive Card renderer above and #13742).
     let actions: Vec<Value> = c
         .links
         .iter()
+        .filter_map(|(label, url)| dispatchable_url(url).map(|url| (label, url)))
         .map(|(label, url)| {
             json!({
                 "@type": "OpenUri",
                 "name": if label.is_empty() { DEFAULT_LINK_LABEL.to_string() } else { escape_html(label) },
-                "targets": [{"os": "default", "uri": safe_url(url)}],
+                "targets": [{"os": "default", "uri": url}],
             })
         })
         .collect();
diff --git a/src/core/src/alerts/notifications/render/webhook.rs b/src/core/src/alerts/notifications/render/webhook.rs
index 97b376e538..00278c8004 100644
--- a/src/core/src/alerts/notifications/render/webhook.rs
+++ b/src/core/src/alerts/notifications/render/webhook.rs
@@ -23,6 +23,23 @@
 //! guarantees a parseable document. Entity-encoding them would corrupt the
 //! data for the machine consumer.
 //!
+//! # Contract: `links[].url` is passed through UNFILTERED — deliberate
+//!
+//! Every human-facing renderer either substitutes a hostile URL scheme
+//! ([`safe_url`], for email/SNS) or drops the link outright
+//! ([`dispatchable_url`], for Slack/Teams/Discord/PagerDuty). This envelope
+//! does NEITHER, for the same reason it does not entity-encode: rewriting a
+//! URL to `#` would hand the consumer corrupted data where it expects the
+//! authored value, and this is a versioned contract other systems parse.
+//!
+//! **The consumer owns presentation and MUST treat `links[].url` as
+//! untrusted.** Save-time validation (`ContentSpec::validate`) rejects a
+//! hostile scheme written literally into a template, but a URL assembled by
+//! variable substitution at send time can still carry one here.
+//!
+//! [`safe_url`]: super::safe_url
+//! [`dispatchable_url`]: super::dispatchable_url
+//!
 //! # Contract: an empty `links[].label` means "no label authored"
 //!
 //! `resolve` appends the alert URL as a link with an EMPTY label. That empty
diff --git a/src/core/src/alerts/notifications/test_send.rs b/src/core/src/alerts/notifications/test_send.rs
index 8ff178a021..8e6510ff9f 100644
--- a/src/core/src/alerts/notifications/test_send.rs
+++ b/src/core/src/alerts/notifications/test_send.rs
@@ -61,6 +61,8 @@ pub enum TestSendError {
     },
     RenderFailed(String),
     DispatchFailed(String),
+    /// Draft fails the same content validation `templates::save` applies.
+    InvalidContent(String),
 }
 
 impl std::fmt::Display for TestSendError {
@@ -73,6 +75,7 @@ impl std::fmt::Display for TestSendError {
             ),
             Self::RenderFailed(e) => write!(f, "test-send render failed: {e}"),
             Self::DispatchFailed(e) => write!(f, "test-send dispatch failed: {e}"),
+            Self::InvalidContent(e) => write!(f, "{e}"),
         }
     }
 }
@@ -161,6 +164,10 @@ fn build_test_message_with_title(
     dest_type: &DestinationType,
     spec: &ContentSpec,
 ) -> Result<(String, RenderedMessage), TestSendError> {
+    // Hold the draft to the same bar `templates::save` applies, so a
+    // test-send cannot "succeed" on a template that cannot be saved.
+    spec.validate().map_err(TestSendError::InvalidContent)?;
+
     let format = derive_channel_format(dest_type);
     let ctx: NotificationContext = synthetic_context(None);
     let mut content = resolve_content(spec, &ctx, format.channel_family());
@@ -227,6 +234,25 @@ mod tests {
         }
     }
 
+    /// A draft whose link scheme `save` would reject must be rejected here
+    /// too, or a test-send "succeeds" on a template that cannot be saved.
+    #[test]
+    fn test_send_rejects_a_draft_the_save_path_would_reject() {
+        let mut spec = sample_spec();
+        spec.links
+            .push(config::meta::alerts::content_spec::ContentLink {
+                label: "click".into(),
+                url: "javascript:alert(1)".into(),
+                show_when: None,
+            });
+        let err = build_test_message(&slack_dest(), &spec)
+            .expect_err("hostile link built a test message cleanly");
+        assert!(
+            err.to_string().contains("click"),
+            "error should name the offending link, got: {err}"
+        );
+    }
+
     #[test]
     fn test_send_title_is_test_marked() {
         let rendered = build_test_message(&slack_dest(), &sample_spec()).unwrap();
diff --git a/src/core/src/alerts/templates.rs b/src/core/src/alerts/templates.rs
index 7f271fbd12..daacf2d9f2 100644
--- a/src/core/src/alerts/templates.rs
+++ b/src/core/src/alerts/templates.rs
@@ -109,8 +109,12 @@ pub async fn save(
     template.kind = resolve_kind(requested_kind, existing_kind, create);
 
     if template.kind == TemplateKind::Content {
-        ContentSpec::parse(&template.body)
+        let spec = ContentSpec::parse(&template.body)
             .map_err(|e| TemplateError::InvalidContentSpec(e.to_string()))?;
+        // Reject an unsupported link scheme HERE rather than neutralizing it
+        // on every send: the author gets a fixable error instead of a
+        // template whose link silently never works (#13742).
+        spec.validate().map_err(TemplateError::InvalidContentSpec)?;
     } else if let TemplateType::Email { title } = &template.template_type
         && title.is_empty()
     {
diff --git a/web/src/components/alerts/AddTemplate.spec.ts b/web/src/components/alerts/AddTemplate.spec.ts
index 401e0ebd5c..4c2fa11664 100644
--- a/web/src/components/alerts/AddTemplate.spec.ts
+++ b/web/src/components/alerts/AddTemplate.spec.ts
@@ -75,8 +75,9 @@ const appTabsStub = {
   emits: ["update:activeTab"],
 };
 
-async function mountComp(props: Record<string, any> = {}) {
+async function mountComp(props: Record<string, any> = {}, opts: Record<string, any> = {}) {
   const wrapper = mount(AddTemplate, {
+    ...opts,
     props: {
       template: null,
       ...props,
@@ -753,3 +754,152 @@ describe("AddTemplate - existing custom template survives a mode-tab round trip"
     expect(getForm(w).state.values.body).toBe(LEGACY_BODY);
   });
 });
+
+// o2-enterprise#2394: clearing the body and saving toasted "Please fill
+// required fields" but left the Monaco editor visually unchanged — the user
+// was told something was wrong with no indication of WHERE. The schema
+// already produces an error on the `body` path; it simply had nowhere to
+// render, because a bare Monaco is bridged in via setFieldValue and is not
+// an OFormInput with an error slot.
+describe("AddTemplate - required-field highlighting on failed save", () => {
+  it("marks the body editor invalid and shows its message when body is empty", async () => {
+    const w = await mountComp();
+    await selectCustomMode(w);
+
+    const form = getForm(w);
+    form.setFieldValue("name", "my-template");
+    form.setFieldValue("body", "");
+    await submit(w);
+
+    // The save must not have gone through.
+    expect(form.state.isValid).toBe(false);
+
+    // The editor must carry a visible error affordance...
+    const shell = w.find('[data-test="add-template-body-editor-shell"]');
+    expect(shell.exists()).toBe(true);
+    expect(shell.attributes("data-error")).toBe("true");
+
+    // ...and a message the user can actually read.
+    const err = w.find('[data-test="add-template-body-error"]');
+    expect(err.exists()).toBe(true);
+    expect(err.text().length).toBeGreaterThan(0);
+  });
+
+  it("clears the body error once a body is typed back in", async () => {
+    const w = await mountComp();
+    await selectCustomMode(w);
+
+    const form = getForm(w);
+    form.setFieldValue("name", "my-template");
+    form.setFieldValue("body", "");
+    await submit(w);
+    expect(w.find('[data-test="add-template-body-error"]').exists()).toBe(true);
+
+    form.setFieldValue("body", '{"text":"hi"}');
+    await flushPromises();
+
+    expect(w.find('[data-test="add-template-body-error"]').exists()).toBe(false);
+    expect(w.find('[data-test="add-template-body-editor-shell"]').attributes("data-error")).toBe(
+      "false",
+    );
+  });
+
+  it("shows no body error before the first save attempt", async () => {
+    const w = await mountComp();
+    await selectCustomMode(w);
+    expect(w.find('[data-test="add-template-body-error"]').exists()).toBe(false);
+  });
+
+  // The aria wiring must live on the SHELL, not on <QueryEditor>:
+  // CodeQueryEditor has `inheritAttrs: false` and binds $attrs to a
+  // non-focusable wrapper, so attributes passed to the component are inert
+  // and would be false assurance for a screen-reader user.
+  it("exposes the error to assistive tech on the shell, not the inert editor", async () => {
+    const w = await mountComp();
+    await selectCustomMode(w);
+
+    const form = getForm(w);
+    form.setFieldValue("name", "my-template");
+    form.setFieldValue("body", "");
+    await submit(w);
+
+    const shell = w.find('[data-test="add-template-body-editor-shell"]');
+    expect(shell.attributes("aria-invalid")).toBe("true");
+    // ...and the described-by must resolve to a node that actually exists.
+    const describedBy = shell.attributes("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    const target = w.find(`#${describedBy}`);
+    expect(target.exists()).toBe(true);
+    expect(target.attributes("role")).toBe("alert");
+  });
+});
+
+// The issue also names the title field. Email templates require a subject;
+// unlike body it IS an OFormInput, so it should already highlight — pin that
+// so the two required fields behave consistently.
+describe("AddTemplate - email title highlighting", () => {
+  it("marks the email title input invalid when it is empty on save", async () => {
+    const w = await mountComp();
+    await selectCustomMode(w);
+
+    const form = getForm(w);
+    form.setFieldValue("type", "email");
+    form.setFieldValue("name", "my-template");
+    form.setFieldValue("body", "hello");
+    form.setFieldValue("title", "");
+    await submit(w);
+
+    expect(form.state.isValid).toBe(false);
+    const err = w.find('[data-test="add-template-email-title-input-error"]');
+    expect(err.exists()).toBe(true);
+    expect(err.text().length).toBeGreaterThan(0);
+  });
+});
+
+// A rejected save must SHOW the user what is wrong. On this form the offending
+// field is often scrolled out of view (the body editor is tall), so the toast
+// alone left them hunting. The first invalid field is scrolled into view.
+describe("AddTemplate - scrolls the first error into view on failed save", () => {
+  it("scrolls to an invalid field when save is rejected", async () => {
+    const scrollSpy = vi.fn();
+    (Element.prototype as any).scrollIntoView = scrollSpy;
+
+    // `attachTo: document.body` is REQUIRED: scrollToFirstError queries the
+    // real document, and a detached wrapper would make it find nothing —
+    // the test would fail while the app works.
+    const w = await mountComp({}, { attachTo: document.body });
+    await selectCustomMode(w);
+
+    // Leave `name` empty so the schema rejects the submit.
+    const form = getForm(w);
+    form.setFieldValue("name", "");
+    form.setFieldValue("body", "");
+    // Click the real Save button: the scroll lives in handleSave, so calling
+    // form.handleSubmit() directly would bypass exactly what we are testing.
+    // Invoke the button's own handler: `trigger("click")` on the OButton
+    // wrapper does not reliably reach the inner <button>, and the behaviour
+    // under test is handleSave's, not Vue's event plumbing.
+    await (w.vm as any).handleSave();
+    await flushPromises();
+    await nextTick();
+
+    expect(form.state.isValid).toBe(false);
+    expect(scrollSpy).toHaveBeenCalled();
+  });
+
+  it("does not scroll when the form is valid", async () => {
+    const scrollSpy = vi.fn();
+    (Element.prototype as any).scrollIntoView = scrollSpy;
+
+    const w = await mountComp({}, { attachTo: document.body });
+    await selectCustomMode(w);
+    const form = getForm(w);
+    form.setFieldValue("name", "valid-name");
+    form.setFieldValue("body", '{"text":"hi"}');
+    await (w.vm as any).handleSave();
+    await flushPromises();
+    await nextTick();
+
+    expect(scrollSpy).not.toHaveBeenCalled();
+  });
+});
diff --git a/web/src/components/alerts/AddTemplate.vue b/web/src/components/alerts/AddTemplate.vue
index 13580595df..09a5ee345d 100644
--- a/web/src/components/alerts/AddTemplate.vue
+++ b/web/src/components/alerts/AddTemplate.vue
@@ -126,15 +126,51 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
                    without this the editor keeps its mount-time language and paints
                    a markdown body with JSON errors (pre-migration got the remount
                    for free from two v-if/v-else editors). -->
-                <QueryEditor
-                  :key="bodyLanguage"
-                  data-test="template-body-editor"
-                  editor-id="template-body-editor"
-                  class="rounded-default border-card-glass-border mb-3 min-h-77.5! w-full resize-y overflow-auto border"
-                  :language="bodyLanguage"
-                  :query="body"
-                  @update:query="onBodyChange"
-                />
+                <!-- The editor is a bare Monaco bridged into the form via
+                   setFieldValue, so it has no OFormInput error slot of its
+                   own. Mirror one here: a red border plus a message, driven
+                   by the `body` field's own validation state, so a rejected
+                   save points AT the offending field (o2-enterprise#2394). -->
+                <!-- `aria-*` goes on this shell, NOT on <QueryEditor>:
+                   CodeQueryEditor sets `inheritAttrs: false` and binds
+                   `$attrs` to a non-focusable wrapper, while Monaco builds
+                   its real textarea in a different child — so attributes
+                   passed to the component would be inert. A `group` with an
+                   accessible name and a described-by is what actually
+                   survives; the message below also carries `role="alert"`,
+                   so it is announced the moment a rejected save renders it. -->
+                <div
+                  data-test="add-template-body-editor-shell"
+                  role="group"
+                  :aria-label="t('alert_templates.body')"
+                  :aria-invalid="bodyError ? 'true' : undefined"
+                  :aria-describedby="bodyError ? 'add-template-body-error' : undefined"
+                  :data-error="String(!!bodyError)"
+                  :class="[
+                    'rounded-default mb-1 w-full overflow-hidden border',
+                    bodyError ? 'border-input-border-error' : 'border-card-glass-border',
+                  ]"
+                >
+                  <QueryEditor
+                    :key="bodyLanguage"
+                    data-test="template-body-editor"
+                    editor-id="template-body-editor"
+                    class="min-h-77.5! w-full resize-y overflow-auto"
+                    :language="bodyLanguage"
+                    :query="body"
+                    @update:query="onBodyChange"
+                  />
+                </div>
+                <div
+                  v-if="bodyError"
+                  id="add-template-body-error"
+                  data-test="add-template-body-error"
+                  class="text-input-error-text mb-3 text-xs"
+                  role="alert"
+                >
+                  {{ bodyError }}
+                </div>
+                <div v-else class="mb-3"></div>
               </div>
             </template>
           </div>
@@ -258,6 +294,8 @@ import OButton from "@/lib/core/Button/OButton.vue";
 import OForm from "@/lib/forms/Form/OForm.vue";
 import OFormInput from "@/lib/forms/Input/OFormInput.vue";
 import { useOForm } from "@/lib/forms/Form/useOForm";
+import { firstFieldError } from "@/lib/forms/Form/fieldError";
+import { scrollToFirstError } from "@/lib/forms/Form/scrollToFirstError";
 import type { TemplateData } from "@/ts/interfaces/index";
 import { useRouter } from "vue-router";
 import AppTabs from "@/components/common/AppTabs.vue";
@@ -281,6 +319,8 @@ import {
 import ContentTemplateForm from "./template-content/ContentTemplateForm.vue";
 import {
   emptyContentSpec,
+  linkUrlBadScheme,
+  NOT_A_URL,
   starterContentSpec,
   parseContentSpec,
   serializeContentSpec,
@@ -326,6 +366,16 @@ const templateType = form.useStore((s: any) => s.values.type as "http" | "email"
 const body = form.useStore((s: any) => (s.values.body as string) ?? "");
 const bodyLanguage = computed(() => (templateType.value === "email" ? "markdown" : "json"));
 
+// The body is a bare Monaco, not an OFormInput, so nothing renders its
+// validation error. Read the SAME field state OFormInput reads
+// (`meta.errors`) and drive a hand-rolled error affordance from it, so an
+// empty body highlights the editor instead of only toasting
+// (o2-enterprise#2394). Validation timing is submit-then-change, so this
+// stays empty until the first save attempt and clears as soon as it is fixed.
+const bodyError = form.useStore((s: any) =>
+  firstFieldError(s.fieldMeta?.body?.errors as readonly unknown[] | undefined),
+);
+
 // app-tabs is a UI toggle whose value is the schema discriminator (not an
 // <input>) → bridge it into the form (sanctioned Rule-② bridge).
 const onTypeChange = (value: unknown) => {
@@ -488,6 +538,10 @@ const handleSave = async () => {
       message: t("common.fillRequiredFields"),
       timeout: 1500,
     });
+    // The offending field is often scrolled off-screen on this form (the body
+    // editor is tall), so the toast alone left the user hunting for what was
+    // wrong. Bring the first invalid field into view and focus it.
+    await scrollToFirstError();
   }
 };
 
@@ -623,6 +677,32 @@ async function saveTemplate(value: AddTemplateForm) {
   // here) so the check never applies to it.
   if (!isContentMode && value.type !== "email" && !isTemplateBodyValid(value.body)) return;
 
+  // Content mode: don't dispatch a save the API will reject with a 400 whose
+  // message is far from the offending field. The inline error under the link
+  // input already says what is wrong (#13742); this stops the round trip and
+  // points at the first bad link.
+  if (isContentMode) {
+    const badLink = contentSpec.value.links
+      .map((l) => ({ link: l, scheme: linkUrlBadScheme(l.url) }))
+      .find((c) => c.scheme);
+    if (badLink?.scheme) {
+      toast({
+        variant: "error",
+        message: t("alerts.validation.linkUrlInvalid", {
+          label: badLink.link.label || t("alert_templates.linkUrl"),
+          reason:
+            badLink.scheme === NOT_A_URL
+              ? t("alerts.validation.linkUrlNotAUrl")
+              : t("alerts.validation.linkUrlUnsupportedScheme", {
+                  scheme: badLink.scheme,
+                }),
+        }),
+      });
+      await scrollToFirstError();
+      return;
+    }
+  }
+
   const dismiss = toast({
     variant: "loading",
     message: t("common.pleaseWait"),
diff --git a/web/src/components/alerts/template-content/ContentFieldsEditor.spec.ts b/web/src/components/alerts/template-content/ContentFieldsEditor.spec.ts
index f18eaed015..5ff45c8fe7 100644
--- a/web/src/components/alerts/template-content/ContentFieldsEditor.spec.ts
+++ b/web/src/components/alerts/template-content/ContentFieldsEditor.spec.ts
@@ -17,7 +17,7 @@ import { describe, expect, it, vi } from "vitest";
 import { mount } from "@vue/test-utils";
 import i18n from "@/locales";
 import ContentFieldsEditor from "./ContentFieldsEditor.vue";
-import type { ContentField } from "./contentSpec";
+import type { ContentField, ContentLink } from "./contentSpec";
 
 function mountEditor(rows: ContentField[]) {
   return mount(ContentFieldsEditor, {
@@ -107,4 +107,52 @@ describe("ContentFieldsEditor", () => {
     const next = w.emitted("update:rows")!.at(-1)![0] as ContentField[];
     expect(next[0].show_when).toBeNull();
   });
+
+  // #13742: a hostile link URL is rejected by the API on save. Surfacing it
+  // inline means the author fixes the right field instead of reading a
+  // whole-form 400.
+  describe("link URL validation (valueKey=url)", () => {
+    function mountLinks(rows: ContentLink[]) {
+      return mount(ContentFieldsEditor, {
+        props: {
+          rows,
+          valueKey: "url",
+          labelLabel: "Label",
+          valueLabel: "URL",
+          addLabel: "Add link",
+          dataTestPrefix: "test-links",
+          "onUpdate:rows": vi.fn(),
+        },
+        global: { plugins: [i18n] },
+      });
+    }
+
+    it("shows an inline error on a link with an unsupported scheme", () => {
+      const w = mountLinks([{ label: "click", url: "javascript:alert(1)" }]);
+      const err = w.find('[data-test="test-links-row-0-value-input-error"]');
+      expect(err.exists()).toBe(true);
+      expect(err.text()).toContain("javascript");
+    });
+
+    it("shows no error for legitimate, templated or relative URLs", () => {
+      const w = mountLinks([
+        { label: "a", url: "https://runbook.example/x" },
+        { label: "b", url: "{alert_url}" },
+        { label: "c", url: "/web/logs" },
+        { label: "d", url: "" },
+      ]);
+      for (const i of [0, 1, 2, 3]) {
+        expect(
+          w.find(`[data-test="test-links-row-${i}-value-input-error"]`).exists(),
+          `row ${i} should have no error`,
+        ).toBe(false);
+      }
+    });
+
+    it("never flags a field value, which has no scheme semantics", () => {
+      // The same component with valueKey="value" must stay unvalidated.
+      const w = mountEditor([{ label: "x", value: "javascript:alert(1)" }]);
+      expect(w.find('[data-test="test-fields-row-0-value-input-error"]').exists()).toBe(false);
+    });
+  });
 });
diff --git a/web/src/components/alerts/template-content/ContentFieldsEditor.vue b/web/src/components/alerts/template-content/ContentFieldsEditor.vue
index a86aa962ca..6fc90c9290 100644
--- a/web/src/components/alerts/template-content/ContentFieldsEditor.vue
+++ b/web/src/components/alerts/template-content/ContentFieldsEditor.vue
@@ -65,6 +65,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
             valueKey === 'value' ? (row as ContentField).value : (row as ContentLink).url
           "
           :placeholder="valuePlaceholder"
+          :error="!!valueErrorFor(row)"
+          :error-message="valueErrorFor(row) ?? undefined"
           :data-test="`${dataTestPrefix}-row-${index}-value-input`"
           @update:model-value="(v) => updateRow(index, valueKey, String(v ?? ''))"
         />
@@ -128,7 +130,7 @@ import { useI18nTyped, type I18nText } from "@/types/i18n";
 import OInput from "@/lib/forms/Input/OInput.vue";
 import OSelect from "@/lib/forms/Select/OSelect.vue";
 import OButton from "@/lib/core/Button/OButton.vue";
-import type { ContentField, ContentLink } from "./contentSpec";
+import { linkUrlBadScheme, NOT_A_URL, type ContentField, type ContentLink } from "./contentSpec";
 
 type RowKind = ContentField | ContentLink;
 
@@ -150,6 +152,19 @@ const emit = defineEmits<{
 
 const { t } = useI18nTyped();
 
+/**
+ * Inline URL validation applies only to the links instance — a field's `value`
+ * is arbitrary text with no scheme semantics. The validator returns the bad
+ * SCHEME, not a message, so the user-facing copy is translated here.
+ */
+function valueErrorFor(row: RowKind): I18nText | undefined {
+  if (props.valueKey !== "url") return undefined;
+  const scheme = linkUrlBadScheme((row as ContentLink).url ?? "");
+  if (!scheme) return undefined;
+  if (scheme === NOT_A_URL) return t("alerts.validation.linkUrlNotAUrl");
+  return t("alerts.validation.linkUrlUnsupportedScheme", { scheme });
+}
+
 // Values are the wire strings the backend's AlertLevel serializes to; the
 // labels a user reads come from i18n, never the wire vocabulary.
 const severityOptions = computed(() => [
diff --git a/web/src/components/alerts/template-content/contentSpec.spec.ts b/web/src/components/alerts/template-content/contentSpec.spec.ts
index a44b26d5d6..d649221f47 100644
--- a/web/src/components/alerts/template-content/contentSpec.spec.ts
+++ b/web/src/components/alerts/template-content/contentSpec.spec.ts
@@ -16,6 +16,8 @@
 import { describe, expect, it } from "vitest";
 import {
   emptyContentSpec,
+  linkUrlBadScheme,
+  NOT_A_URL,
   starterContentSpec,
   hasOptionalContent,
   parseContentSpec,
@@ -216,4 +218,93 @@ describe("contentSpec", () => {
       expect(hasOptionalContent(starterContentSpec())).toBe(true);
     });
   });
+
+  // Mirrors the backend allowlist in
+  // src/config/src/meta/alerts/content_spec.rs — these cases are kept in sync
+  // deliberately so the inline error and the API's 400 agree. The backend
+  // remains the enforcing layer; this only moves the message next to the field.
+  describe("linkUrlBadScheme", () => {
+    it("rejects active-content schemes, including blocklist bypasses", () => {
+      for (const hostile of [
+        "javascript:alert(1)",
+        "JavaScript:alert(1)",
+        "  javascript:alert(1)",
+        "java\tscript:alert(1)",
+        "java\nscript:alert(1)",
+        "\0javascript:alert(1)",
+        "java%73cript:alert(1)",
+        "vbscript:msgbox(1)",
+        "file:///etc/passwd",
+        "data:text/html,<script>1",
+        // A variable elsewhere does not excuse a literal hostile scheme.
+        "{x}javascript:alert(1)",
+        // Trailing whitespace must not smuggle a scheme past the check.
+        "javascript:alert(1)   ",
+      ]) {
+        expect(linkUrlBadScheme(hostile), `accepted: ${hostile}`).toBeTruthy();
+      }
+    });
+
+    // A link field holds a URL. These cannot execute anything (no scheme), but
+    // they are not links either — accepting them means the author finds out
+    // the link is dead when an alert fires.
+    it("rejects values that are not URLs at all", () => {
+      for (const junk of [
+        "javascript(0)",
+        "not a url at all",
+        "foo",
+        "runbook.example.com/x", // bare host: ambiguous, require a scheme
+        // An allowlisted scheme with NO HOST. Per the WHATWG URL Standard an
+        // empty host is a parse FAILURE for a special scheme (http/https).
+        "http:",
+        "http://",
+        "https://",
+        "http:///",
+        "http://?q=1",
+        "http://#frag",
+        // Hosts that parse but cannot resolve to anything real.
+        "https://.",
+        "http://..",
+        "https://-",
+        // `mailto:` needs a real mailbox; the parser accepts any opaque path.
+        "mailto:",
+        "mailto:foo",
+        "mailto:@",
+        "mailto:a@",
+        "mailto:@b.com",
+        "{x} not a url",
+      ]) {
+        expect(linkUrlBadScheme(junk), `accepted: ${junk}`).toBe(NOT_A_URL);
+      }
+    });
+
+    it("accepts legitimate, templated and relative URLs", () => {
+      for (const ok of [
+        "https://runbook.example/x",
+        "http://runbook.example/x",
+        "mailto:oncall@example.com",
+        "https://runbook.example/{stream_name}",
+        "{alert_url}",
+        "{alert_url}&tab=logs",
+        "{scheme}://host/x", // variable IN scheme position
+        "/web/logs?stream=app",
+        "HTTPS://runbook.example/x", // schemes are case-insensitive
+        "MAILTO:oncall@example.com",
+        "  https://runbook.example/x  ", // surrounding whitespace is trimmed
+        "https://o2.example:8443/web/logs?a=1#f",
+        "http://localhost:5080/web/logs",
+        "https://user:pass@host.example/x", // userinfo is legal
+        "https://[::1]:8080/x", // IPv6 literal
+        "https://192.168.1.1/x", // IPv4 literal
+        // U+0085 (NEL) is Unicode White_Space, so Rust's `.trim()` strips it
+        // and the backend accepts this. JS `.trim()` does NOT strip NEL, so
+        // without an explicit class here the UI would flag a URL the API
+        // saves happily — the frontend must not be stricter than the server.
+        `${String.fromCharCode(0x85)}https://runbook.example/x`,
+        "", // an empty row is not an error — it is simply not filled in yet
+      ]) {
+        expect(linkUrlBadScheme(ok), `rejected: ${ok}`).toBeNull();
+      }
+    });
+  });
 });
diff --git a/web/src/components/alerts/template-content/contentSpec.ts b/web/src/components/alerts/template-content/contentSpec.ts
index 0613733dbb..c5800faef3 100644
--- a/web/src/components/alerts/template-content/contentSpec.ts
+++ b/web/src/components/alerts/template-content/contentSpec.ts
@@ -171,6 +171,104 @@ export function hasOptionalContent(spec: ContentSpec): boolean {
   );
 }
 
+/**
+ * Schemes a link URL may carry, mirroring the backend allowlist in
+ * `src/config/src/meta/alerts/content_spec.rs`.
+ */
+const ALLOWED_LINK_SCHEMES = ["http", "https", "mailto"];
+
+/**
+ * Sentinel returned by {@link linkUrlBadScheme} when the value is not a URL at
+ * all (a bare word like `foo`), as opposed to a URL carrying a disallowed
+ * scheme. The caller picks a different message for each.
+ */
+export const NOT_A_URL = "\u0000not-a-url";
+
+/**
+ * The offending scheme when a link URL is unacceptable, or null when it is
+ * fine. Returns the SCHEME rather than a message so the caller can translate:
+ * user-facing copy is `I18nText`, and baking English in here would leak it
+ * into every non-English org.
+ *
+ * This is a UX affordance, NOT the security boundary — the backend rejects the
+ * same URLs on save (HTTP 400) and the renderers drop undeliverable ones at
+ * send time. Its job is to put the message next to the offending field instead
+ * of surfacing a whole-form API error.
+ *
+ * An allowlist rather than a blocklist, matching the backend: `java\tscript:`,
+ * `\0javascript:`, `java%73cript:` and `vbscript:` all slip past a naive
+ * `startsWith("javascript:")` while a browser still dispatches them.
+ *
+ * Deliberately permitted, because the backend permits them too:
+ * - empty — an unfilled row is incomplete, not invalid
+ * - `{alert_url}` — link URLs are templates; the scheme may only exist after variable substitution
+ * - `/path`, `?q=1`, `#frag` — relative URLs are inert and valid in email
+ */
+export function linkUrlBadScheme(url: string): string | null {
+  // Rust's `str::trim` strips every Unicode `White_Space` char; JS `.trim()`
+  // strips `WhiteSpace` + `LineTerminator`, which OMITS U+0085 (NEL). Without
+  // the explicit NEL class a URL carrying one would be flagged here and
+  // accepted by the backend. Keep in step with `link_scheme_is_allowed`.
+  const trimmed = url.replace(/^[\s\u0085]+|[\s\u0085]+$/g, "");
+
+  // Not filled in yet - incomplete, not invalid.
+  if (trimmed === "") return null; // Whitespace and control characters are never valid inside a URL. Tested by
+  // codepoint rather than a regex: a control-character class in a literal
+  // trips `no-control-regex`, and these are exactly what must be rejected.
+  for (const ch of trimmed) {
+    const c = ch.codePointAt(0)!;
+    if (c <= 0x20 || c === 0x7f) return NOT_A_URL;
+  }
+
+  // A ":" only introduces a scheme when it precedes any path/query/fragment
+  // marker (RFC 3986), so "/a:b" is a scheme-less path, not a scheme.
+  const boundary = trimmed.search(/[:/?#]/);
+  if (boundary === -1 || trimmed[boundary] !== ":") {
+    // No scheme: accept a root-relative reference, or a template whose scheme
+    // only materializes after substitution. A bare word ("foo",
+    // "javascript(0)") is a typo, not a link - see the Rust twin.
+    if (/^[/?#]/.test(trimmed)) return null;
+    return /^\{[^}]+\}/.test(trimmed) ? null : NOT_A_URL;
+  }
+
+  const rawScheme = trimmed.slice(0, boundary);
+
+  // A scheme that is ENTIRELY a variable has nothing to judge yet, but
+  // "{x}javascript:" must still be rejected - see the Rust twin.
+  if (rawScheme.startsWith("{") && rawScheme.endsWith("}") && !rawScheme.slice(1).includes("{")) {
+    return null;
+  }
+
+  const scheme = rawScheme.toLowerCase();
+  if (!ALLOWED_LINK_SCHEMES.includes(scheme)) return scheme;
+
+  // An allowlisted scheme is necessary but NOT sufficient: `http:` and
+  // `https://` carry one and are still not URLs (an empty host is a parse
+  // FAILURE for a special scheme per the WHATWG URL Standard). Delegate to
+  // the platform's conformant parser instead of hand-rolling it.
+  let parsed: URL;
+  try {
+    parsed = new URL(trimmed);
+  } catch {
+    return NOT_A_URL;
+  }
+
+  if (scheme === "mailto") {
+    // The parser accepts ANY opaque path after `mailto:`, including an empty
+    // one, so the mailbox shape is checked here.
+    const at = parsed.pathname.indexOf("@");
+    if (at <= 0) return NOT_A_URL;
+    const domain = parsed.pathname.slice(at + 1);
+    return domain.includes(".") && !domain.startsWith(".") ? null : NOT_A_URL;
+  }
+
+  // http(s): reject hosts that parse but can never resolve (".", "..", "-").
+  const host = parsed.hostname;
+  const hostOk =
+    host.length > 0 && /[a-z0-9]/i.test(host) && !/^[.-]/.test(host) && !/[.-]$/.test(host);
+  return hostOk ? null : NOT_A_URL;
+}
+
 export function serializeContentSpec(spec: ContentSpec): string {
   // Trim only the body's leading/trailing whitespace on save — not on every
   // keystroke or blur, so the live editor (blank lines, toolbar cursor
diff --git a/web/src/components/cross-linking/CrossLinkDialog.schema.spec.ts b/web/src/components/cross-linking/CrossLinkDialog.schema.spec.ts
new file mode 100644
index 0000000000..4724c8c1d2
--- /dev/null
+++ b/web/src/components/cross-linking/CrossLinkDialog.schema.spec.ts
@@ -0,0 +1,50 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import { describe, expect, it } from "vitest";
+import { crossLinkUrlIsValid } from "./CrossLinkDialog.schema";
+
+// A cross-link URL is handed to window.open for EVERY viewer of the stream,
+// and previously the only rule was `min(1)`.
+describe("crossLinkUrlIsValid", () => {
+  it("accepts http(s) templates with ${field} placeholders", () => {
+    for (const ok of [
+      "https://example.com/trace/${field.__value}",
+      "https://example.com/x?from=${start_time}&to=${end_time}",
+      "http://localhost:5080/web/logs",
+      "https://example.com",
+    ]) {
+      expect(crossLinkUrlIsValid(ok), `rejected: ${ok}`).toBe(true);
+    }
+  });
+
+  it("rejects hostile schemes", () => {
+    for (const bad of [
+      "javascript:alert(1)",
+      "javascript:alert(document.cookie)",
+      "data:text/html,<script>alert(1)</script>",
+      "file:///etc/passwd",
+      "vbscript:msgbox(1)",
+    ]) {
+      expect(crossLinkUrlIsValid(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects values that are not URLs", () => {
+    for (const bad of ["foo", "not a url", "http:", "http://", "https://."]) {
+      expect(crossLinkUrlIsValid(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+});
diff --git a/web/src/components/cross-linking/CrossLinkDialog.schema.ts b/web/src/components/cross-linking/CrossLinkDialog.schema.ts
index 8d79adb686..8ce77f2e81 100644
--- a/web/src/components/cross-linking/CrossLinkDialog.schema.ts
+++ b/web/src/components/cross-linking/CrossLinkDialog.schema.ts
@@ -8,10 +8,28 @@
 
 import { z } from "zod";
 
+import { isSafeNavigableUrl } from "@/utils/safeUrl";
+
+/**
+ * A cross-link URL is a TEMPLATE containing `${field.__value}` placeholders,
+ * so it is validated with the placeholders stripped to a harmless token — the
+ * shape around them still has to be a real http(s) URL.
+ *
+ * Previously the only rule was `min(1)`, so `javascript:alert(1)` saved
+ * cleanly and was handed to `window.open` for every viewer of the stream.
+ */
+export function crossLinkUrlIsValid(url: string): boolean {
+  const withoutPlaceholders = url.replace(/\$\{[^}]*\}/g, "x");
+  return isSafeNavigableUrl(withoutPlaceholders);
+}
+
 export const makeCrossLinkDialogSchema = (t: (_key: string) => string) =>
   z.object({
     name: z.string().min(1, t("crossLinks.nameRequired")),
-    url: z.string().min(1, t("crossLinks.urlRequired")),
+    url: z
+      .string()
+      .min(1, t("crossLinks.urlRequired"))
+      .refine(crossLinkUrlIsValid, { message: t("crossLinks.urlInvalid") }),
     fields: z.array(z.object({ name: z.string() })).default([]),
     // Chip-builder scratch input that stages a field name before it's committed
     // as a chip. NOT part of the emit payload; form-owned + optional.
diff --git a/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.spec.ts b/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.spec.ts
new file mode 100644
index 0000000000..bcbb55bf42
--- /dev/null
+++ b/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.spec.ts
@@ -0,0 +1,50 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import { describe, expect, it } from "vitest";
+import { drilldownUrlIsValid } from "./DrilldownPopUp.schema";
+
+describe("drilldownUrlIsValid", () => {
+  it("accepts http(s) templates with ${variable} placeholders", () => {
+    for (const ok of [
+      "https://example.com/d/${value}",
+      "https://example.com/x?a=${row.field}",
+      "http://localhost:5080/web/logs",
+    ]) {
+      expect(drilldownUrlIsValid(ok), `rejected: ${ok}`).toBe(true);
+    }
+  });
+
+  // The previous regex named these schemes as ALLOWED. `window.open` is called
+  // on this value, so data:/file: are navigable targets, not inert text.
+  it("rejects schemes the old protocol regex explicitly allowed", () => {
+    for (const bad of [
+      "data:text/html;base64,PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg==",
+      "file:///etc/passwd",
+      "telnet://host",
+      "ws://host/x",
+      "wss://host/x",
+      "ftp://host/x",
+    ]) {
+      expect(drilldownUrlIsValid(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects hostile schemes and non-URLs", () => {
+    for (const bad of ["javascript:alert(1)", "foo", "http://", "https://-"]) {
+      expect(drilldownUrlIsValid(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+});
diff --git a/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.ts b/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.ts
index 86d02adac7..430c927bd2 100644
--- a/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.ts
+++ b/web/src/components/dashboards/addPanel/DrilldownPopUp.schema.ts
@@ -20,8 +20,22 @@
 
 import { z } from "zod";
 
-// Protocol-only URL check.
-const URL_PROTOCOL_REGEX = /^(http|https|ftp|file|mailto|telnet|data|ws|wss):\/\//;
+import { isSafeNavigableUrl } from "@/utils/safeUrl";
+
+/**
+ * A drilldown URL is a TEMPLATE containing `${variable}` placeholders, so it
+ * is validated with the placeholders stripped to a harmless token — the shape
+ * around them still has to be a real http(s) URL.
+ *
+ * This replaces a scheme-prefix regex that allowed `ftp`, `file`, `telnet`,
+ * `data`, `ws` and `wss` by name. `data:` and `file:` are navigable targets
+ * (`usePanelDrilldown` calls `window.open` on this value), and the regex also
+ * passed degenerate values like `http://` that are not URLs at all.
+ */
+export function drilldownUrlIsValid(url: string): boolean {
+  const withoutPlaceholders = url.replace(/\$\{[^}]*\}/g, "x");
+  return isSafeNavigableUrl(withoutPlaceholders);
+}
 
 // Array row — kept loose (no per-row rules).
 export const drilldownVariableRowSchema = z.object({
@@ -73,7 +87,7 @@ export const makeDrilldownPopUpSchema = (t: (_key: string) => string) =>
             path: ["data", "url"],
             message: t("dashboard.urlRequired"),
           });
-        } else if (!URL_PROTOCOL_REGEX.test(url)) {
+        } else if (!drilldownUrlIsValid(url)) {
           ctx.addIssue({
             code: z.ZodIssueCode.custom,
             path: ["data", "url"],
diff --git a/web/src/composables/dashboard/usePanelDrilldown.ts b/web/src/composables/dashboard/usePanelDrilldown.ts
index 12baba50db..2ad619ed29 100644
--- a/web/src/composables/dashboard/usePanelDrilldown.ts
+++ b/web/src/composables/dashboard/usePanelDrilldown.ts
@@ -20,6 +20,7 @@ import { getUTCTimestampFromZonedTimestamp } from "@/utils/dashboard/dateTimeUti
 import { normalizeVariableSyntax } from "@/utils/dashboard/variables/variablesUtils";
 import searchService from "@/services/search";
 import { isCrossLinkingEnabledForStream } from "@/utils/crossLinking";
+import { isSafeNavigableUrl } from "@/utils/safeUrl";
 
 export function usePanelDrilldown({
   panelSchema,
@@ -932,10 +933,17 @@ export function usePanelDrilldown({
       // if drilldown by url
       if (drilldownData.type == "byUrl") {
         try {
+          // Guard the RESOLVED url. The form schema rejects a hostile one at
+          // save time, but that is client-side only: a direct dashboard PUT
+          // stores anything, and dashboards saved before the schema existed
+          // are still in the DB. A variable VALUE can also carry a scheme.
+          const resolved = replacePlaceholders(drilldownData.data.url, drilldownVariables);
+          if (!isSafeNavigableUrl(resolved)) return;
           // open url
           return window.open(
-            replacePlaceholders(drilldownData.data.url, drilldownVariables),
+            resolved,
             drilldownData.targetBlank ? "_blank" : "_self",
+            "noopener,noreferrer",
           );
         } catch {
           /* ignore: best-effort window.open */
diff --git a/web/src/lib/forms/Form/scrollToFirstError.spec.ts b/web/src/lib/forms/Form/scrollToFirstError.spec.ts
new file mode 100644
index 0000000000..a6e092f450
--- /dev/null
+++ b/web/src/lib/forms/Form/scrollToFirstError.spec.ts
@@ -0,0 +1,107 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { scrollToFirstError } from "./scrollToFirstError";
+
+describe("scrollToFirstError", () => {
+  beforeEach(() => {
+    document.body.innerHTML = "";
+    // A single prototype stub is shared by every element, so "not called"
+    // could never distinguish them — give each element its own spy.
+    (Element.prototype as any).scrollIntoView = function () {};
+  });
+
+  function field(id: string, invalid: boolean) {
+    const el = document.createElement("input");
+    el.id = id;
+    if (invalid) el.setAttribute("aria-invalid", "true");
+    el.scrollIntoView = vi.fn();
+    document.body.appendChild(el);
+    return el;
+  }
+
+  it("scrolls the FIRST invalid control into view, not a later one", async () => {
+    field("ok", false);
+    const first = field("bad-1", true);
+    const second = field("bad-2", true);
+
+    const scrolled = await scrollToFirstError();
+
+    expect(scrolled).toBe(true);
+    expect(first.scrollIntoView).toHaveBeenCalled();
+    expect(second.scrollIntoView).not.toHaveBeenCalled();
+  });
+
+  it("focuses the field so the user can start typing the fix", async () => {
+    const el = field("bad", true);
+    const focus = vi.spyOn(el, "focus");
+    await scrollToFirstError();
+    expect(focus).toHaveBeenCalled();
+  });
+
+  it("returns false and does nothing when no field is invalid", async () => {
+    const el = field("ok", false);
+    expect(await scrollToFirstError()).toBe(false);
+    expect(el.scrollIntoView).not.toHaveBeenCalled();
+  });
+
+  it('ignores aria-invalid="false" — only true marks an error', async () => {
+    const el = field("ok", false);
+    el.setAttribute("aria-invalid", "false");
+    expect(await scrollToFirstError()).toBe(false);
+    expect(el.scrollIntoView).not.toHaveBeenCalled();
+  });
+
+  it("falls back to a non-focusable error container when no control is invalid", async () => {
+    // The Monaco body editor is not a focusable control; its error state lives
+    // on a wrapper (o2-enterprise#2394), which must still be scrolled to.
+    const shell = document.createElement("div");
+    shell.setAttribute("data-error", "true");
+    shell.scrollIntoView = vi.fn();
+    document.body.appendChild(shell);
+
+    expect(await scrollToFirstError()).toBe(true);
+    expect(shell.scrollIntoView).toHaveBeenCalled();
+  });
+
+  it("prefers a real invalid control over a data-error container", async () => {
+    const shell = document.createElement("div");
+    shell.setAttribute("data-error", "true");
+    shell.scrollIntoView = vi.fn();
+    document.body.appendChild(shell);
+    const input = field("bad", true);
+
+    await scrollToFirstError();
+
+    expect(input.scrollIntoView).toHaveBeenCalled();
+    expect(shell.scrollIntoView).not.toHaveBeenCalled();
+  });
+
+  it("searches only within the given root when one is passed", async () => {
+    const outside = field("outside-bad", true);
+    const root = document.createElement("div");
+    const inside = document.createElement("input");
+    inside.setAttribute("aria-invalid", "true");
+    inside.scrollIntoView = vi.fn();
+    root.appendChild(inside);
+    document.body.appendChild(root);
+
+    await scrollToFirstError(root);
+
+    expect(inside.scrollIntoView).toHaveBeenCalled();
+    expect(outside.scrollIntoView).not.toHaveBeenCalled();
+  });
+});
diff --git a/web/src/lib/forms/Form/scrollToFirstError.ts b/web/src/lib/forms/Form/scrollToFirstError.ts
new file mode 100644
index 0000000000..797c3f3fb4
--- /dev/null
+++ b/web/src/lib/forms/Form/scrollToFirstError.ts
@@ -0,0 +1,57 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import { nextTick } from "vue";
+
+/**
+ * Bring the first invalid field into view after a rejected submit.
+ *
+ * On a long form the failing field is often scrolled off-screen, so the user
+ * gets "Please fill required fields" with nothing visibly wrong — they cannot
+ * tell WHICH field, or even that the page has more of it above. Scrolling the
+ * offender into view and focusing it turns a dead-end toast into an actionable
+ * one.
+ *
+ * Selection order:
+ *
+ * 1. `[aria-invalid="true"]` — every `OInput`-based control sets this, so it covers all standard
+ *    fields and is framework-agnostic (no per-form field registry to keep in sync).
+ * 2. `[data-error="true"]` — a non-focusable wrapper for controls that are not real form elements,
+ *    e.g. the Monaco body editor (o2-enterprise#2394), which has no focusable node of its own to
+ *    mark.
+ *
+ * Awaits `nextTick` first: validation state is applied during the same tick as
+ * the submit, so querying before the DOM updates would find nothing.
+ *
+ * @param root Limit the search to this subtree. Defaults to the whole document.
+ * @returns whether a field was found and scrolled to.
+ */
+export async function scrollToFirstError(root?: ParentNode): Promise<boolean> {
+  await nextTick();
+
+  const scope = root ?? document;
+  const target =
+    scope.querySelector<HTMLElement>('[aria-invalid="true"]') ??
+    scope.querySelector<HTMLElement>('[data-error="true"]');
+
+  if (!target) return false;
+
+  target.scrollIntoView({ behavior: "smooth", block: "center" });
+  // Focus so the user can start typing the fix immediately. Guarded: the
+  // fallback target is a wrapper div, which is not focusable.
+  target.focus?.({ preventScroll: true });
+
+  return true;
+}
diff --git a/web/src/lib/forms/Input/OInput.spec.ts b/web/src/lib/forms/Input/OInput.spec.ts
index 3804292497..8913608fb6 100644
--- a/web/src/lib/forms/Input/OInput.spec.ts
+++ b/web/src/lib/forms/Input/OInput.spec.ts
@@ -45,6 +45,43 @@ describe("OInput", () => {
     expect(wrapper.text()).toContain("Required field");
   });
 
+  it("points aria-describedby at the error message so it is announced", () => {
+    wrapper = mount(OInput, { props: { error: true, errorMessage: "Required field" } });
+    const input = wrapper.find("input");
+    const describedBy = input.attributes("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    expect(input.attributes("aria-invalid")).toBe("true");
+    // The referenced node must actually exist and carry the message —
+    // a dangling aria-describedby announces nothing.
+    const target = wrapper.find(`#${describedBy}`);
+    expect(target.exists()).toBe(true);
+    expect(target.text()).toContain("Required field");
+  });
+
+  it("sets no aria-describedby when there is no error to describe", () => {
+    wrapper = mount(OInput, { props: { errorMessage: "Required field" } });
+    expect(wrapper.find("input").attributes("aria-describedby")).toBeUndefined();
+  });
+
+  it("sets no dangling aria-describedby when the message is rendered elsewhere", () => {
+    // `error` with no `errorMessage` yields " " — OFormInput's #error slot owns
+    // the text, so this component renders no message node to point at.
+    wrapper = mount(OInput, { props: { error: true } });
+    expect(wrapper.find("input").attributes("aria-describedby")).toBeUndefined();
+    expect(wrapper.find("input").attributes("aria-invalid")).toBe("true");
+  });
+
+  it("describes the textarea variant too", () => {
+    wrapper = mount(OInput, {
+      props: { type: "textarea", error: true, errorMessage: "Too long" },
+    });
+    const ta = wrapper.find("textarea");
+    expect(ta.attributes("aria-invalid")).toBe("true");
+    const describedBy = ta.attributes("aria-describedby");
+    expect(describedBy).toBeTruthy();
+    expect(wrapper.find(`#${describedBy}`).text()).toContain("Too long");
+  });
+
   it("shows helpText when provided", () => {
     wrapper = mount(OInput, { props: { helpText: "Enter your name" } });
     expect(wrapper.text()).toContain("Enter your name");
diff --git a/web/src/lib/forms/Input/OInput.vue b/web/src/lib/forms/Input/OInput.vue
index 3683a37b8f..04b0f41fce 100644
--- a/web/src/lib/forms/Input/OInput.vue
+++ b/web/src/lib/forms/Input/OInput.vue
@@ -70,6 +70,16 @@ const effectiveError = computed(() => {
 });
 const hasError = computed(() => !!effectiveError.value);
 
+// `aria-invalid` alone tells a screen reader THAT the field is wrong but never
+// WHAT is wrong. Point the control at the message element so the reason is
+// announced with the field. Only set when a message is actually rendered —
+// `effectiveError` is " " when the text lives in OFormInput's #error slot, and
+// a dangling `aria-describedby` would reference a node that does not exist.
+const errorId = computed(() => `${inputId.value}-error`);
+const describedBy = computed(() =>
+  effectiveError.value && effectiveError.value.trim() ? errorId.value : undefined,
+);
+
 const isTextarea = computed(() => props.type === "textarea");
 
 // ── Width ──────────────────────────────────────────────────────────────────
@@ -298,6 +308,8 @@ const wrapperClasses = computed(() => [
         :disabled="disabled"
         :readonly="readonly"
         :aria-required="required || undefined"
+        :aria-invalid="hasError || undefined"
+        :aria-describedby="describedBy"
         :autofocus="autofocus"
         :maxlength="maxlength"
         :rows="autogrow ? 1 : rows"
@@ -341,6 +353,7 @@ const wrapperClasses = computed(() => [
         :autocomplete="autocomplete"
         :tabindex="inputTabindex"
         :aria-invalid="hasError || undefined"
+        :aria-describedby="describedBy"
         :class="[
           'min-w-0 flex-1 rounded-[inherit] bg-transparent outline-none',
           'text-input-text placeholder:text-input-placeholder',
@@ -413,6 +426,7 @@ const wrapperClasses = computed(() => [
     >
       <span
         v-if="effectiveError && effectiveError.trim()"
+        :id="errorId"
         :data-test="parentDataTest ? `${parentDataTest}-error` : undefined"
         :data-test-error-text="effectiveError"
         class="text-input-error-text text-xs leading-none"
diff --git a/web/src/locales/languages/de-DE.json b/web/src/locales/languages/de-DE.json
index 8cbb84f144..5a8b0c623f 100644
--- a/web/src/locales/languages/de-DE.json
+++ b/web/src/locales/languages/de-DE.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Ungültige VRL-Funktion",
       "invalidSqlQuery": "Ungültige SQL-Abfrage",
       "errorFetchingStreams": "Fehler beim Abrufen der Streams",
-      "sqlValidationError": "SQL-Validierungsfehler: {error}"
+      "sqlValidationError": "SQL-Validierungsfehler: {error}",
+      "linkUrlUnsupportedScheme": "Nicht unterstütztes URL-Schema \"{scheme}\". Verwenden Sie http, https oder mailto — ein relativer Pfad oder eine {'{'}Variable{'}'} funktioniert ebenfalls.",
+      "linkUrlInvalid": "Link \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Geben Sie eine gültige URL ein — z. B. https://example.com/runbook, einen Pfad wie /web/logs oder eine {'{'}Variable{'}'}."
     },
     "header": "Warnmeldungen",
     "subtitle": "Alarmregeln und Benachrichtigungskanäle",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "URL-Vorlage",
     "urlRequired": "URL ist erforderlich",
     "urlPlaceholder": "z. B. https://example.com/trace/{'${field.__value}'}?von={'${start_time}'}&bis={'${end_time}'}",
+    "urlInvalid": "Geben Sie eine gültige http(s)-URL ein",
     "urlHint": "Verwenden Sie {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Felder",
     "fieldsHint": "Link nur anzeigen, wenn mindestens ein Feld im Datensatz vorhanden ist",
diff --git a/web/src/locales/languages/en-US.json b/web/src/locales/languages/en-US.json
index 556ca01d70..d3bfbe7728 100644
--- a/web/src/locales/languages/en-US.json
+++ b/web/src/locales/languages/en-US.json
@@ -5334,7 +5334,10 @@
       "invalidSqlQuery": "Invalid SQL Query",
       "errorFetchingStreams": "Error fetching streams",
       "sqlValidationError": "SQL validation error: {error}",
-      "nameUnsupportedChars": "Alert names cannot contain spaces or : # ? ' \" % & /"
+      "nameUnsupportedChars": "Alert names cannot contain spaces or : # ? ' \" % & /",
+      "linkUrlUnsupportedScheme": "Unsupported URL scheme \"{scheme}\". Use http, https or mailto — a relative path or a {'{'}variable{'}'} also works.",
+      "linkUrlInvalid": "Link \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Enter a valid URL — for example https://example.com/runbook, a path like /web/logs, or a {'{'}variable{'}'}."
     },
     "header": "Alerts",
     "subtitle": "Alert rules and notification channels",
@@ -8701,6 +8704,7 @@
     "urlTemplate": "URL Template",
     "urlRequired": "URL is required",
     "urlPlaceholder": "e.g., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Enter a valid http(s) URL",
     "urlHint": "Use {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Fields",
     "fieldsHint": "Show link only when at least one field is present in the record",
diff --git a/web/src/locales/languages/es-ES.json b/web/src/locales/languages/es-ES.json
index 146a5038dd..c5b8e8f4c2 100644
--- a/web/src/locales/languages/es-ES.json
+++ b/web/src/locales/languages/es-ES.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Función VRL no válida",
       "invalidSqlQuery": "Consulta SQL no válida",
       "errorFetchingStreams": "Error al obtener los flujos",
-      "sqlValidationError": "Error de validación SQL: {error}"
+      "sqlValidationError": "Error de validación SQL: {error}",
+      "linkUrlUnsupportedScheme": "Esquema de URL no admitido \"{scheme}\". Use http, https o mailto: una ruta relativa o una {'{'}variable{'}'} también funciona.",
+      "linkUrlInvalid": "Enlace \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Introduzca una URL válida: por ejemplo https://example.com/runbook, una ruta como /web/logs o una {'{'}variable{'}'}."
     },
     "header": "Alertas",
     "subtitle": "Reglas de alertas y canales de notificación",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Plantilla de URL",
     "urlRequired": "La URL es obligatoria",
     "urlPlaceholder": "p. ej., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Introduzca una URL http(s) válida",
     "urlHint": "Usa {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Campos",
     "fieldsHint": "Mostrar enlace solo cuando hay al menos un campo en el registro",
diff --git a/web/src/locales/languages/fr-FR.json b/web/src/locales/languages/fr-FR.json
index de1f579a36..de36218229 100644
--- a/web/src/locales/languages/fr-FR.json
+++ b/web/src/locales/languages/fr-FR.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Fonction VRL invalide",
       "invalidSqlQuery": "Requête SQL invalide",
       "errorFetchingStreams": "Erreur lors de la récupération des flux",
-      "sqlValidationError": "Erreur de validation SQL : {error}"
+      "sqlValidationError": "Erreur de validation SQL : {error}",
+      "linkUrlUnsupportedScheme": "Schéma d'URL non pris en charge \"{scheme}\". Utilisez http, https ou mailto — un chemin relatif ou une {'{'}variable{'}'} fonctionne aussi.",
+      "linkUrlInvalid": "Lien \"{label}\" : {reason}",
+      "linkUrlNotAUrl": "Saisissez une URL valide — par exemple https://example.com/runbook, un chemin comme /web/logs ou une {'{'}variable{'}'}."
     },
     "header": "Alertes",
     "subtitle": "Règles d'alerte et canaux de notification",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Modèle d'URL",
     "urlRequired": "L'URL est obligatoire",
     "urlPlaceholder": "par ex., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Saisissez une URL http(s) valide",
     "urlHint": "Utilisez {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Champs",
     "fieldsHint": "Afficher le lien uniquement lorsqu'au moins un champ est présent dans l'enregistrement",
diff --git a/web/src/locales/languages/it-IT.json b/web/src/locales/languages/it-IT.json
index aaf527f3d9..341bd0a745 100644
--- a/web/src/locales/languages/it-IT.json
+++ b/web/src/locales/languages/it-IT.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Funzione VRL non valida",
       "invalidSqlQuery": "Query SQL non valida",
       "errorFetchingStreams": "Errore nel recupero degli stream",
-      "sqlValidationError": "Errore di validazione SQL: {error}"
+      "sqlValidationError": "Errore di validazione SQL: {error}",
+      "linkUrlUnsupportedScheme": "Schema URL non supportato \"{scheme}\". Usa http, https o mailto: funziona anche un percorso relativo o una {'{'}variabile{'}'}.",
+      "linkUrlInvalid": "Link \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Inserisci un URL valido — ad esempio https://example.com/runbook, un percorso come /web/logs o una {'{'}variabile{'}'}."
     },
     "header": "Avvisi",
     "subtitle": "Regole di avviso e canali di notifica",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Template URL",
     "urlRequired": "L'URL è obbligatorio",
     "urlPlaceholder": "ad es., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Inserisci un URL http(s) valido",
     "urlHint": "Usa {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Campi",
     "fieldsHint": "Mostra il link solo quando nel record è presente almeno un campo",
diff --git a/web/src/locales/languages/ja-JP.json b/web/src/locales/languages/ja-JP.json
index 3bc73e3927..f807c67853 100644
--- a/web/src/locales/languages/ja-JP.json
+++ b/web/src/locales/languages/ja-JP.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "無効なVRL関数です",
       "invalidSqlQuery": "無効なSQLクエリです",
       "errorFetchingStreams": "ストリームの取得中にエラーが発生しました",
-      "sqlValidationError": "SQL検証エラー: {error}"
+      "sqlValidationError": "SQL検証エラー: {error}",
+      "linkUrlUnsupportedScheme": "サポートされていない URL スキーム \"{scheme}\" です。http、https、mailto を使用してください。相対パスや {'{'}変数{'}'} も使用できます。",
+      "linkUrlInvalid": "リンク \"{label}\": {reason}",
+      "linkUrlNotAUrl": "有効な URL を入力してください。例: https://example.com/runbook、/web/logs のようなパス、または {'{'}変数{'}'}。"
     },
     "header": "アラート",
     "subtitle": "アラートルールと通知チャネル",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "URL テンプレート",
     "urlRequired": "URL が必要です",
     "urlPlaceholder": "例: https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "有効な http(s) URL を入力してください",
     "urlHint": "{'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'} を使用",
     "fields": "フィールド",
     "fieldsHint": "レコードに少なくとも 1 つのフィールドが存在する場合にのみリンクを表示",
diff --git a/web/src/locales/languages/ko-KR.json b/web/src/locales/languages/ko-KR.json
index aa13b2ee0c..e9fa2f278d 100644
--- a/web/src/locales/languages/ko-KR.json
+++ b/web/src/locales/languages/ko-KR.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "잘못된 VRL 함수",
       "invalidSqlQuery": "잘못된 SQL 쿼리",
       "errorFetchingStreams": "스트림 가져오기 오류",
-      "sqlValidationError": "SQL 유효성 검사 오류: {error}"
+      "sqlValidationError": "SQL 유효성 검사 오류: {error}",
+      "linkUrlUnsupportedScheme": "지원되지 않는 URL 스킴 \"{scheme}\"입니다. http, https 또는 mailto를 사용하세요. 상대 경로나 {'{'}변수{'}'}도 사용할 수 있습니다.",
+      "linkUrlInvalid": "링크 \"{label}\": {reason}",
+      "linkUrlNotAUrl": "유효한 URL을 입력하세요. 예: https://example.com/runbook, /web/logs 같은 경로 또는 {'{'}변수{'}'}."
     },
     "header": "알림",
     "subtitle": "경고 규칙 및 알림 채널",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "URL 템플릿",
     "urlRequired": "URL이 필요합니다",
     "urlPlaceholder": "예: https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "유효한 http(s) URL을 입력하세요",
     "urlHint": "{'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'} 사용",
     "fields": "필드",
     "fieldsHint": "레코드에 하나 이상의 필드가 있는 경우에만 링크 표시",
diff --git a/web/src/locales/languages/nl-NL.json b/web/src/locales/languages/nl-NL.json
index 3eccf6f5dc..9678aa737f 100644
--- a/web/src/locales/languages/nl-NL.json
+++ b/web/src/locales/languages/nl-NL.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Ongeldige VRL-functie",
       "invalidSqlQuery": "Ongeldige SQL-query",
       "errorFetchingStreams": "Fout bij ophalen van streams",
-      "sqlValidationError": "SQL-validatiefout: {error}"
+      "sqlValidationError": "SQL-validatiefout: {error}",
+      "linkUrlUnsupportedScheme": "Niet-ondersteund URL-schema \"{scheme}\". Gebruik http, https of mailto — een relatief pad of een {'{'}variabele{'}'} werkt ook.",
+      "linkUrlInvalid": "Link \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Voer een geldige URL in — bijvoorbeeld https://example.com/runbook, een pad zoals /web/logs of een {'{'}variabele{'}'}."
     },
     "header": "Alarmen",
     "subtitle": "Waarschuwingsregels en meldingskanalen",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "URL-sjabloon",
     "urlRequired": "URL is vereist",
     "urlPlaceholder": "bijv. https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Voer een geldige http(s)-URL in",
     "urlHint": "Gebruik {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Velden",
     "fieldsHint": "Link alleen tonen als er minstens één veld in de record aanwezig is",
diff --git a/web/src/locales/languages/pl-PL.json b/web/src/locales/languages/pl-PL.json
index 25f5315d99..58cb74f161 100644
--- a/web/src/locales/languages/pl-PL.json
+++ b/web/src/locales/languages/pl-PL.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Nieprawidłowa funkcja VRL",
       "invalidSqlQuery": "Nieprawidłowe zapytanie SQL",
       "errorFetchingStreams": "Błąd podczas pobierania strumieni",
-      "sqlValidationError": "Błąd walidacji SQL: {error}"
+      "sqlValidationError": "Błąd walidacji SQL: {error}",
+      "linkUrlUnsupportedScheme": "Nieobsługiwany schemat URL \"{scheme}\". Użyj http, https lub mailto — działa też ścieżka względna lub {'{'}zmienna{'}'}.",
+      "linkUrlInvalid": "Link \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Podaj prawidłowy adres URL — na przykład https://example.com/runbook, ścieżkę taką jak /web/logs lub {'{'}zmienną{'}'}."
     },
     "header": "Alerty",
     "subtitle": "Reguły alertów i kanały powiadomień",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Szablon URL",
     "urlRequired": "URL jest wymagany",
     "urlPlaceholder": "np. https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Podaj prawidłowy adres URL http(s)",
     "urlHint": "Użyj {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Pola",
     "fieldsHint": "Pokaż link tylko gdy co najmniej jedno pole jest obecne w rekordzie",
diff --git a/web/src/locales/languages/pt-PT.json b/web/src/locales/languages/pt-PT.json
index 3518576f79..8954eee983 100644
--- a/web/src/locales/languages/pt-PT.json
+++ b/web/src/locales/languages/pt-PT.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Função VRL inválida",
       "invalidSqlQuery": "Consulta SQL inválida",
       "errorFetchingStreams": "Erro ao buscar streams",
-      "sqlValidationError": "Erro de validação SQL: {error}"
+      "sqlValidationError": "Erro de validação SQL: {error}",
+      "linkUrlUnsupportedScheme": "Esquema de URL não suportado \"{scheme}\". Use http, https ou mailto — um caminho relativo ou uma {'{'}variável{'}'} também funciona.",
+      "linkUrlInvalid": "Ligação \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Introduza um URL válido — por exemplo https://example.com/runbook, um caminho como /web/logs ou uma {'{'}variável{'}'}."
     },
     "header": "Alertas",
     "subtitle": "Regras de alerta e canais de notificação",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Modelo de URL",
     "urlRequired": "O URL é obrigatório",
     "urlPlaceholder": "ex., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Introduza um URL http(s) válido",
     "urlHint": "Use {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Campos",
     "fieldsHint": "Mostrar link somente quando pelo menos um campo estiver presente no registro",
diff --git a/web/src/locales/languages/ru-RU.json b/web/src/locales/languages/ru-RU.json
index 4a810ee951..c2ddc1bb20 100644
--- a/web/src/locales/languages/ru-RU.json
+++ b/web/src/locales/languages/ru-RU.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Некорректная функция VRL",
       "invalidSqlQuery": "Некорректный SQL-запрос",
       "errorFetchingStreams": "Ошибка получения потоков",
-      "sqlValidationError": "Ошибка проверки SQL: {error}"
+      "sqlValidationError": "Ошибка проверки SQL: {error}",
+      "linkUrlUnsupportedScheme": "Неподдерживаемая схема URL \"{scheme}\". Используйте http, https или mailto — также подойдёт относительный путь или {'{'}переменная{'}'}.",
+      "linkUrlInvalid": "Ссылка \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Введите корректный URL — например https://example.com/runbook, путь вида /web/logs или {'{'}переменную{'}'}."
     },
     "header": "Оповещения",
     "subtitle": "Правила оповещений и каналы уведомлений",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Шаблон URL",
     "urlRequired": "URL обязателен",
     "urlPlaceholder": "например, https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Введите корректный http(s) URL",
     "urlHint": "Используйте {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Поля",
     "fieldsHint": "Показывать ссылку только если хотя бы одно поле присутствует в записи",
diff --git a/web/src/locales/languages/tr-TR.json b/web/src/locales/languages/tr-TR.json
index 33c5d110d4..c4bf720f42 100644
--- a/web/src/locales/languages/tr-TR.json
+++ b/web/src/locales/languages/tr-TR.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Geçersiz VRL İşlevi",
       "invalidSqlQuery": "Geçersiz SQL Sorgusu",
       "errorFetchingStreams": "Akışlar alınırken hata",
-      "sqlValidationError": "SQL doğrulama hatası: {error}"
+      "sqlValidationError": "SQL doğrulama hatası: {error}",
+      "linkUrlUnsupportedScheme": "Desteklenmeyen URL şeması \"{scheme}\". http, https veya mailto kullanın — göreli bir yol ya da {'{'}değişken{'}'} de çalışır.",
+      "linkUrlInvalid": "Bağlantı \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Geçerli bir URL girin — örneğin https://example.com/runbook, /web/logs gibi bir yol veya bir {'{'}değişken{'}'}."
     },
     "header": "Uyarılar",
     "subtitle": "Uyarı kuralları ve bildirim kanalları",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "URL Şablonu",
     "urlRequired": "URL gerekli",
     "urlPlaceholder": "örn., https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Geçerli bir http(s) URL girin",
     "urlHint": "{'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'} kullanın",
     "fields": "Tarlalar",
     "fieldsHint": "Bağlantıyı yalnızca kayıtta en az bir alan varsa göster",
diff --git a/web/src/locales/languages/vi-VN.json b/web/src/locales/languages/vi-VN.json
index 2f3e0c4f85..ce067ad7f6 100644
--- a/web/src/locales/languages/vi-VN.json
+++ b/web/src/locales/languages/vi-VN.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "Hàm VRL không hợp lệ",
       "invalidSqlQuery": "Truy vấn SQL không hợp lệ",
       "errorFetchingStreams": "Lỗi khi tải danh sách luồng",
-      "sqlValidationError": "Lỗi xác thực SQL: {error}"
+      "sqlValidationError": "Lỗi xác thực SQL: {error}",
+      "linkUrlUnsupportedScheme": "Lược đồ URL không được hỗ trợ \"{scheme}\". Hãy dùng http, https hoặc mailto — đường dẫn tương đối hoặc {'{'}biến{'}'} cũng được.",
+      "linkUrlInvalid": "Liên kết \"{label}\": {reason}",
+      "linkUrlNotAUrl": "Nhập một URL hợp lệ — ví dụ https://example.com/runbook, đường dẫn như /web/logs, hoặc một {'{'}biến{'}'}."
     },
     "header": "Cảnh báo",
     "subtitle": "Quy tắc cảnh báo và kênh thông báo",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "Mẫu URL",
     "urlRequired": "Yêu cầu nhập URL",
     "urlPlaceholder": "ví dụ: https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "Nhập một URL http(s) hợp lệ",
     "urlHint": "Sử dụng {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "Trường",
     "fieldsHint": "Chỉ hiển thị liên kết khi có ít nhất một trường trong bản ghi",
diff --git a/web/src/locales/languages/zh-CN.json b/web/src/locales/languages/zh-CN.json
index a9fe9ea166..3f413c8285 100644
--- a/web/src/locales/languages/zh-CN.json
+++ b/web/src/locales/languages/zh-CN.json
@@ -5306,7 +5306,10 @@
       "invalidVrlFunction": "VRL 函数无效",
       "invalidSqlQuery": "SQL 查询无效",
       "errorFetchingStreams": "获取流时出错",
-      "sqlValidationError": "SQL 验证错误：{error}"
+      "sqlValidationError": "SQL 验证错误：{error}",
+      "linkUrlUnsupportedScheme": "不支持的 URL 协议 \"{scheme}\"。请使用 http、https 或 mailto — 相对路径或 {'{'}变量{'}'} 也可以。",
+      "linkUrlInvalid": "链接 \"{label}\"：{reason}",
+      "linkUrlNotAUrl": "请输入有效的 URL — 例如 https://example.com/runbook、类似 /web/logs 的路径，或 {'{'}变量{'}'}。"
     },
     "header": "告警",
     "subtitle": "警报规则和通知渠道",
@@ -8659,6 +8662,7 @@
     "urlTemplate": "网址模板",
     "urlRequired": "网址为必填项",
     "urlPlaceholder": "例如，https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "请输入有效的 http(s) URL",
     "urlHint": "使用 {'${field.__name}'}, {'${field.__value}'}, {'${start_time}'}, {'${end_time}'}, {'${query}'}, {'${query_encoded}'}",
     "fields": "字段",
     "fieldsHint": "仅当记录中至少存在一个字段时才显示链接",
diff --git a/web/src/locales/languages/zh-TW.json b/web/src/locales/languages/zh-TW.json
index 2cd0a3c5db..320dd000aa 100644
--- a/web/src/locales/languages/zh-TW.json
+++ b/web/src/locales/languages/zh-TW.json
@@ -5301,7 +5301,10 @@
       "invalidVrlFunction": "無效的 VRL 函數",
       "invalidSqlQuery": "無效的 SQL 查詢",
       "errorFetchingStreams": "取得串流時發生錯誤",
-      "sqlValidationError": "SQL 驗證錯誤：{error}"
+      "sqlValidationError": "SQL 驗證錯誤：{error}",
+      "linkUrlUnsupportedScheme": "不支援的 URL 協定 \"{scheme}\"。請使用 http、https 或 mailto — 相對路徑或 {'{'}變數{'}'} 也可以。",
+      "linkUrlInvalid": "連結 \"{label}\"：{reason}",
+      "linkUrlNotAUrl": "請輸入有效的 URL — 例如 https://example.com/runbook、類似 /web/logs 的路徑，或 {'{'}變數{'}'}。"
     },
     "header": "警示",
     "subtitle": "警報規則與通知管道",
@@ -8654,6 +8657,7 @@
     "urlTemplate": "URL 範本",
     "urlRequired": "URL 為必填",
     "urlPlaceholder": "例如 https://example.com/trace/{'${field.__value}'}?from={'${start_time}'}&to={'${end_time}'}",
+    "urlInvalid": "請輸入有效的 http(s) URL",
     "urlHint": "使用 {'${field.__name}'}、{'${field.__value}'}、{'${start_time}'}、{'${end_time}'}、{'${query}'}、{'${query_encoded}'}",
     "fields": "欄位",
     "fieldsHint": "僅當記錄中存在至少一個欄位時顯示連結",
diff --git a/web/src/plugins/logs/DetailTable.spec.ts b/web/src/plugins/logs/DetailTable.spec.ts
index f14c5016b9..ae545b5f93 100644
--- a/web/src/plugins/logs/DetailTable.spec.ts
+++ b/web/src/plugins/logs/DetailTable.spec.ts
@@ -951,7 +951,33 @@ describe("DetailTable Component", () => {
       const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
       wrapper.vm.openCrossLink("https://example.com/trace/123");
 
-      expect(openSpy).toHaveBeenCalledWith("https://example.com/trace/123", "_blank");
+      // `noopener,noreferrer` stops the opened tab reaching back via
+      // window.opener and strips the referrer.
+      expect(openSpy).toHaveBeenCalledWith(
+        "https://example.com/trace/123",
+        "_blank",
+        "noopener,noreferrer",
+      );
+      openSpy.mockRestore();
+    });
+
+    // The RESOLVED url is guarded, not just the saved template: links stored
+    // before save-time validation existed are still in the DB, and a field
+    // VALUE substituted into a template can carry a hostile scheme.
+    it("does not open a cross-link whose resolved url is unsafe", () => {
+      const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+
+      for (const hostile of [
+        "javascript:alert(document.cookie)",
+        "data:text/html,<script>alert(1)</script>",
+        "file:///etc/passwd",
+        "http://",
+        "not a url",
+      ]) {
+        wrapper.vm.openCrossLink(hostile);
+      }
+
+      expect(openSpy).not.toHaveBeenCalled();
       openSpy.mockRestore();
     });
 
diff --git a/web/src/plugins/logs/DetailTable.vue b/web/src/plugins/logs/DetailTable.vue
index b9440a7008..57468ba8d9 100644
--- a/web/src/plugins/logs/DetailTable.vue
+++ b/web/src/plugins/logs/DetailTable.vue
@@ -471,6 +471,7 @@ import OIcon from "@/lib/core/Icon/OIcon.vue";
 import OTable from "@/lib/core/Table/OTable.vue";
 import OSearchInput from "@/lib/forms/SearchInput/OSearchInput.vue";
 import OSeparator from "@/lib/core/Separator/OSeparator.vue";
+import { isSafeNavigableUrl } from "@/utils/safeUrl";
 const defaultValue: any = () => {
   return {
     data: {},
@@ -922,7 +923,9 @@ export default defineComponent({
     };
 
     const openCrossLink = (url: string) => {
-      window.open(url, "_blank");
+      // Guard the RESOLVED url — see JsonPreview.vue's twin for the reasoning.
+      if (!isSafeNavigableUrl(url)) return;
+      window.open(url, "_blank", "noopener,noreferrer");
     };
 
     const viewTrace = () => {
diff --git a/web/src/plugins/logs/JsonPreview.spec.ts b/web/src/plugins/logs/JsonPreview.spec.ts
index 1696b42980..6775a16dab 100644
--- a/web/src/plugins/logs/JsonPreview.spec.ts
+++ b/web/src/plugins/logs/JsonPreview.spec.ts
@@ -1130,7 +1130,33 @@ describe("JsonPreview Component", () => {
       const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
       wrapper.vm.openCrossLink("https://example.com/trace/123");
 
-      expect(openSpy).toHaveBeenCalledWith("https://example.com/trace/123", "_blank");
+      // `noopener,noreferrer` stops the opened tab reaching back via
+      // window.opener and strips the referrer.
+      expect(openSpy).toHaveBeenCalledWith(
+        "https://example.com/trace/123",
+        "_blank",
+        "noopener,noreferrer",
+      );
+      openSpy.mockRestore();
+    });
+
+    // See the DetailTable twin: the RESOLVED url is guarded, because links
+    // saved before validation existed are still in the DB and a substituted
+    // field VALUE can carry a hostile scheme.
+    it("does not open a cross-link whose resolved url is unsafe", () => {
+      const openSpy = vi.spyOn(window, "open").mockImplementation(() => null);
+
+      for (const hostile of [
+        "javascript:alert(document.cookie)",
+        "data:text/html,<script>alert(1)</script>",
+        "file:///etc/passwd",
+        "http://",
+        "not a url",
+      ]) {
+        wrapper.vm.openCrossLink(hostile);
+      }
+
+      expect(openSpy).not.toHaveBeenCalled();
       openSpy.mockRestore();
     });
 
diff --git a/web/src/plugins/logs/JsonPreview.vue b/web/src/plugins/logs/JsonPreview.vue
index d4bd31b9c0..0601fdaeae 100644
--- a/web/src/plugins/logs/JsonPreview.vue
+++ b/web/src/plugins/logs/JsonPreview.vue
@@ -280,6 +280,7 @@ import OSelect from "@/lib/forms/Select/OSelect.vue";
 import { copyToClipboard } from "@/utils/clipboard";
 import { timestampToTimezoneDate } from "@/utils/timezone";
 import { toast } from "@/lib/feedback/Toast/useToast";
+import { isSafeNavigableUrl } from "@/utils/safeUrl";
 
 export default {
   name: "JsonPreview",
@@ -485,7 +486,14 @@ export default {
     const crossLinkDropdownVisible = ref(false);
 
     const openCrossLink = (url: string) => {
-      window.open(url, "_blank");
+      // Guard the RESOLVED url, not just the saved template: links stored
+      // before save-time validation existed are still in the DB, and a field
+      // VALUE substituted into the template can carry a hostile scheme too.
+      if (!isSafeNavigableUrl(url)) {
+        crossLinkDropdownVisible.value = false;
+        return;
+      }
+      window.open(url, "_blank", "noopener,noreferrer");
       crossLinkDropdownVisible.value = false;
     };
     let multiStreamFields: any = ref([]);
diff --git a/web/src/utils/common.spec.ts b/web/src/utils/common.spec.ts
index 838a9c7a92..6ea0c766f0 100644
--- a/web/src/utils/common.spec.ts
+++ b/web/src/utils/common.spec.ts
@@ -38,6 +38,9 @@ describe("Common Utils", () => {
     Object.defineProperty(window, "location", {
       value: {
         href: "",
+        // `origin` is what the same-origin redirect check compares against;
+        // a real window.location always has it.
+        origin: "http://localhost:3000",
         replace: vi.fn(),
       },
       writable: true,
@@ -175,12 +178,26 @@ describe("Common Utils", () => {
       mockZincutils.getPath = vi.fn().mockReturnValue("/default-path");
     });
 
-    it("should redirect to external URL when redirectURI contains http", () => {
-      const externalUrl = "https://external-site.com/redirect";
+    // SECURITY: `redirectURI` comes from the attacker-controllable
+    // `?short_url=` query param. It previously only had to CONTAIN "http",
+    // so an off-origin URL sent the user to a phishing site right after they
+    // authenticated. Off-origin must now fall back to the home path.
+    it("refuses an off-origin redirect and goes to the default path instead", () => {
+      const replaceSpy = vi.spyOn(window.location, "replace");
 
-      redirectUser(externalUrl);
+      redirectUser("https://external-site.com/redirect");
 
-      expect(window.location.href).toBe(externalUrl);
+      expect(replaceSpy).toHaveBeenCalledWith("/default-path");
+      expect(window.location.href).not.toContain("external-site.com");
+    });
+
+    it("refuses protocol-relative and backslash off-origin tricks", () => {
+      for (const hostile of ["//evil.com/", "/\\evil.com", "https://localhost.evil.com/"]) {
+        const replaceSpy = vi.spyOn(window.location, "replace");
+        redirectUser(hostile);
+        expect(replaceSpy, `accepted: ${hostile}`).toHaveBeenCalledWith("/default-path");
+        replaceSpy.mockRestore();
+      }
     });
 
     it("should use replace for internal redirects", () => {
@@ -209,20 +226,12 @@ describe("Common Utils", () => {
       expect(replaceSpy).toHaveBeenCalledWith("/default-path");
     });
 
-    it("should handle https URLs", () => {
-      const httpsUrl = "https://secure.example.com/auth";
+    it("still allows an absolute URL on the SAME origin", () => {
+      const sameOrigin = "http://localhost:3000/auth/callback";
 
-      redirectUser(httpsUrl);
+      redirectUser(sameOrigin);
 
-      expect(window.location.href).toBe(httpsUrl);
-    });
-
-    it("should handle http URLs", () => {
-      const httpUrl = "http://example.com/redirect";
-
-      redirectUser(httpUrl);
-
-      expect(window.location.href).toBe(httpUrl);
+      expect(window.location.href).toBe(sameOrigin);
     });
 
     it("should handle relative paths", () => {
diff --git a/web/src/utils/common.ts b/web/src/utils/common.ts
index 2bff4e517a..de05aaeb07 100644
--- a/web/src/utils/common.ts
+++ b/web/src/utils/common.ts
@@ -16,6 +16,7 @@
 import { ref } from "vue";
 import organizationsService from "../services/organizations";
 import { useLocalOrganization, getPath } from "./zincutils";
+import { isSameOriginRedirect } from "@/utils/safeUrl";
 
 const selectedOrg = ref("");
 const orgOptions = ref([{ label: Number, value: String }]);
@@ -71,11 +72,21 @@ export const getDefaultOrganization = async (userInfo: any, org_identifier: any)
 
 export const redirectUser = (redirectURI: string | null) => {
   const path = getPath();
+  // `redirectURI` comes from the `?short_url=` query param (router/index.ts),
+  // so it is attacker-controllable. The previous check was
+  // `redirectURI.includes("http")` — a substring test that happily matched
+  // `https://evil.com/` and sent the user off-site immediately AFTER they
+  // authenticated. Anything not on this origin falls back to the home path.
   if (redirectURI != null && redirectURI != "") {
-    if (redirectURI.includes("http")) {
-      window.location.href = redirectURI;
-    } else {
+    if (!isSameOriginRedirect(redirectURI)) {
+      // Off-origin: refuse it and go home instead.
+      window.location.replace(path);
+    } else if (redirectURI.startsWith("/")) {
+      // Relative path — keep using `replace` so the login page does not stay
+      // in history (unchanged from the original behaviour).
       window.location.replace(redirectURI);
+    } else {
+      window.location.href = redirectURI;
     }
   } else {
     // $router.push({ path: "/" });
diff --git a/web/src/utils/safeUrl.spec.ts b/web/src/utils/safeUrl.spec.ts
new file mode 100644
index 0000000000..18e8f35780
--- /dev/null
+++ b/web/src/utils/safeUrl.spec.ts
@@ -0,0 +1,125 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import { describe, expect, it } from "vitest";
+import { isSafeNavigableUrl, isSameOriginRedirect } from "./safeUrl";
+
+describe("isSafeNavigableUrl", () => {
+  it("accepts absolute http(s) URLs", () => {
+    for (const ok of [
+      "https://example.com",
+      "http://example.com/path?q=1#f",
+      "https://example.com:8443/x",
+      "https://user:pass@example.com/x",
+      "https://192.168.1.1/x",
+      "https://[::1]:8080/x",
+      "HTTPS://EXAMPLE.COM/X",
+    ]) {
+      expect(isSafeNavigableUrl(ok), `rejected: ${ok}`).toBe(true);
+    }
+  });
+
+  it("rejects active-content schemes, including blocklist bypasses", () => {
+    for (const bad of [
+      "javascript:alert(1)",
+      "JavaScript:alert(1)",
+      "  javascript:alert(1)",
+      "java\tscript:alert(1)",
+      "java\nscript:alert(1)",
+      "\u0000javascript:alert(1)",
+      "vbscript:msgbox(1)",
+      // Explicitly allowed by the old drilldown regex — both are unsafe.
+      "data:text/html;base64,PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg==",
+      "file:///etc/passwd",
+      "telnet://host",
+      "ws://host",
+    ]) {
+      expect(isSafeNavigableUrl(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects an allowlisted scheme with no host (a WHATWG parse failure)", () => {
+    for (const bad of ["http:", "http://", "https://", "http:///", "http://?q=1", "http://#f"]) {
+      expect(isSafeNavigableUrl(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects hosts that parse but cannot resolve", () => {
+    for (const bad of ["https://.", "http://..", "https://-", "http://.:80"]) {
+      expect(isSafeNavigableUrl(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects values that are not URLs at all", () => {
+    for (const bad of ["", "   ", "foo", "javascript(0)", "not a url at all"]) {
+      expect(isSafeNavigableUrl(bad), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("optionally allows mailto: for link targets", () => {
+    expect(isSafeNavigableUrl("mailto:on@call.com")).toBe(false);
+    expect(isSafeNavigableUrl("mailto:on@call.com", { allowMailto: true })).toBe(true);
+    // Still needs a real mailbox.
+    expect(isSafeNavigableUrl("mailto:", { allowMailto: true })).toBe(false);
+    expect(isSafeNavigableUrl("mailto:foo", { allowMailto: true })).toBe(false);
+  });
+
+  it("optionally allows a {variable} template that resolves at render time", () => {
+    expect(isSafeNavigableUrl("{alert_url}")).toBe(false);
+    expect(isSafeNavigableUrl("{alert_url}", { allowTemplateVars: true })).toBe(true);
+    expect(isSafeNavigableUrl("https://x.example/{field}", { allowTemplateVars: true })).toBe(true);
+    // A variable elsewhere does not excuse a literal hostile scheme.
+    expect(isSafeNavigableUrl("{x}javascript:alert(1)", { allowTemplateVars: true })).toBe(false);
+  });
+});
+
+describe("isSameOriginRedirect", () => {
+  const ORIGIN = "https://app.example.com";
+
+  it("accepts a relative path", () => {
+    for (const ok of ["/web/logs", "/", "/a?b=1#c"]) {
+      expect(isSameOriginRedirect(ok, ORIGIN), `rejected: ${ok}`).toBe(true);
+    }
+  });
+
+  it("accepts an absolute URL on the SAME origin", () => {
+    expect(isSameOriginRedirect(`${ORIGIN}/web/logs`, ORIGIN)).toBe(true);
+  });
+
+  it("rejects an absolute URL on a DIFFERENT origin", () => {
+    // The old check was `redirectURI.includes("http")`, which let every one
+    // of these through and redirected the user off-site after login.
+    for (const bad of [
+      "https://evil.com/",
+      "http://evil.com/",
+      "https://app.example.com.evil.com/", // lookalike host
+      "//evil.com/", // protocol-relative
+      "https://app.example.com:8443/x", // different port = different origin
+    ]) {
+      expect(isSameOriginRedirect(bad, ORIGIN), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects hostile schemes and backslash tricks", () => {
+    for (const bad of ["javascript:alert(1)", "data:text/html,x", "\\\\evil.com", "/\\evil.com"]) {
+      expect(isSameOriginRedirect(bad, ORIGIN), `accepted: ${bad}`).toBe(false);
+    }
+  });
+
+  it("rejects empty/nullish input", () => {
+    expect(isSameOriginRedirect("", ORIGIN)).toBe(false);
+    expect(isSameOriginRedirect(null, ORIGIN)).toBe(false);
+  });
+});
diff --git a/web/src/utils/safeUrl.ts b/web/src/utils/safeUrl.ts
new file mode 100644
index 0000000000..7c2bb2da39
--- /dev/null
+++ b/web/src/utils/safeUrl.ts
@@ -0,0 +1,133 @@
+// Copyright 2026 OpenObserve Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// One place to answer "is this user-supplied string a URL we may navigate to?"
+//
+// This check had been written from scratch four times (`safeHttpUrl` in
+// ingestion/setupCard/subs.ts, `getHttpUrl` in TableRenderer.vue, and twice in
+// the synthetics schemas), and the two places that DIDN'T have it — dashboard
+// drilldowns and stream cross-links — are exactly where unsafe values got in.
+// Prefer this helper over a fifth hand-rolled regex.
+
+/** Schemes that may ever be navigated to. NOT data:, file:, ws:, telnet:. */
+const NAVIGABLE_SCHEMES = ["http:", "https:"];
+
+export interface SafeUrlOptions {
+  /** Also accept `mailto:` with a real `local@domain` mailbox. */
+  allowMailto?: boolean;
+  /**
+   * Also accept a value whose scheme only materializes after `{variable}`
+   * substitution at render time (alert templates, drilldowns, cross-links).
+   * A literal hostile scheme is still rejected: `{x}javascript:` fails.
+   */
+  allowTemplateVars?: boolean;
+}
+
+/**
+ * True when `value` is a URL that is safe to navigate to (`window.open`,
+ * `location.href`, an `:href` binding).
+ *
+ * Why a parser and not a regex: a scheme allowlist alone is not enough —
+ * `http:` and `https://` carry an allowlisted scheme and are still not URLs
+ * (per the WHATWG URL Standard an empty host is a *parse failure* for a
+ * special scheme). And a parser alone is not enough either — `javascript:`
+ * parses perfectly well. Both checks are required, in that order.
+ */
+export function isSafeNavigableUrl(value: unknown, opts: SafeUrlOptions = {}): boolean {
+  if (typeof value !== "string") return false;
+  const trimmed = value.trim();
+  if (trimmed === "") return false;
+
+  // Control characters and internal whitespace are never valid in a URL, and
+  // are how `java\tscript:` style bypasses are smuggled past naive checks.
+  for (const ch of trimmed) {
+    const c = ch.codePointAt(0)!;
+    if (c <= 0x20 || c === 0x7f) return false;
+  }
+
+  if (opts.allowTemplateVars) {
+    // A variable in SCHEME POSITION defers judgement to substitution time.
+    // Deliberately strict: `{x}javascript:alert(1)` also starts with `{`, but
+    // the rest of its scheme is the literal, hostile `javascript`, so the
+    // variable must be the WHOLE scheme (or the whole value).
+    const boundary = trimmed.search(/[:/?#]/);
+    const schemeIsVariable =
+      boundary === -1
+        ? /^\{[^{}]+\}/.test(trimmed) // no scheme at all: `{alert_url}&tab=x`
+        : trimmed[boundary] === ":" && /^\{[^{}]+\}$/.test(trimmed.slice(0, boundary));
+    if (schemeIsVariable) return true;
+  }
+
+  let parsed: URL;
+  try {
+    parsed = new URL(trimmed);
+  } catch {
+    return false;
+  }
+
+  const scheme = parsed.protocol.toLowerCase();
+
+  if (scheme === "mailto:") {
+    if (!opts.allowMailto) return false;
+    const at = parsed.pathname.indexOf("@");
+    if (at <= 0) return false;
+    const domain = parsed.pathname.slice(at + 1);
+    return domain.includes(".") && !domain.startsWith(".");
+  }
+
+  if (!NAVIGABLE_SCHEMES.includes(scheme)) return false;
+
+  // `new URL()` guarantees a non-empty host for a special scheme, but a host
+  // may still be junk that can never resolve (".", "..", "-").
+  const host = parsed.hostname;
+  return host.length > 0 && /[a-z0-9]/i.test(host) && !/^[.-]/.test(host) && !/[.-]$/.test(host);
+}
+
+/**
+ * True when `value` is safe to redirect to after login — a relative path, or
+ * an absolute URL on `origin` itself.
+ *
+ * The previous check was `redirectURI.includes("http")`, a substring test that
+ * accepted `https://evil.com/` and sent the user off-site immediately after
+ * authenticating (the classic post-auth phishing setup).
+ */
+export function isSameOriginRedirect(
+  value: string | null | undefined,
+  origin: string = window.location.origin,
+): boolean {
+  if (!value) return false;
+  const trimmed = value.trim();
+  if (trimmed === "") return false;
+
+  for (const ch of trimmed) {
+    const c = ch.codePointAt(0)!;
+    if (c <= 0x20 || c === 0x7f) return false;
+  }
+
+  // A backslash is normalized to `/` by browsers, so `/\evil.com` and
+  // `\\evil.com` are protocol-relative in disguise.
+  if (trimmed.includes("\\")) return false;
+  // Protocol-relative (`//evil.com`) points off-origin despite looking relative.
+  if (trimmed.startsWith("//")) return false;
+
+  // Plain relative path: same origin by construction.
+  if (trimmed.startsWith("/")) return true;
+
+  try {
+    return new URL(trimmed, origin).origin === new URL(origin).origin;
+  } catch {
+    return false;
+  }
+}
diff --git a/web/src/views/Login.spec.ts b/web/src/views/Login.spec.ts
index 872df87554..4cf45442db 100644
--- a/web/src/views/Login.spec.ts
+++ b/web/src/views/Login.spec.ts
@@ -435,20 +435,24 @@ describe("Login.vue", () => {
       expect(pushSpy).toHaveBeenCalledWith({ path: "/dashboard" });
     });
 
-    it("should redirect to external URL when redirectURI contains http", async () => {
-      // Mock azure_marketplace_token as null so it checks redirectURI
+    // SECURITY: `redirectURI` originates from the attacker-controllable
+    // `?short_url=` query param, so an OFF-ORIGIN value here is a post-auth
+    // open redirect (phishing). It must be refused and routed home instead.
+    it("refuses an off-origin redirect and routes to the home path", async () => {
       mockSessionStorage.getItem.mockImplementation((key: string) => {
         if (key === "azure_marketplace_token") return null;
         if (key === "redirectURI") return "https://external.com";
         return null;
       });
 
+      const pushSpy = vi.spyOn(router, "push");
+
       wrapper.vm.redirectUser();
 
       expect(mockSessionStorage.getItem).toHaveBeenCalledWith("azure_marketplace_token");
-      expect(mockSessionStorage.getItem).toHaveBeenCalledWith("redirectURI");
       expect(mockSessionStorage.removeItem).toHaveBeenCalledWith("redirectURI");
-      expect(window.location.href).toBe("https://external.com");
+      expect(window.location.href).not.toBe("https://external.com");
+      expect(pushSpy).toHaveBeenCalledWith({ path: "/" });
     });
 
     it("should redirect to home when no redirectURI", async () => {
diff --git a/web/src/views/Login.vue b/web/src/views/Login.vue
index d2d753a2e0..c7f2edda2f 100644
--- a/web/src/views/Login.vue
+++ b/web/src/views/Login.vue
@@ -58,6 +58,7 @@ import {
 import { useReo } from "@/services/reodotdev_analytics";
 import { toast } from "@/lib/feedback/Toast/useToast";
 import { useI18nTyped } from "@/types/i18n";
+import { isSameOriginRedirect } from "@/utils/safeUrl";
 
 export default defineComponent({
   name: "LoginPage",
@@ -233,11 +234,14 @@ export default defineComponent({
 
       const redirectURI = window.sessionStorage.getItem("redirectURI");
       window.sessionStorage.removeItem("redirectURI");
-      if (redirectURI != null && redirectURI != "") {
-        if (redirectURI.includes("http")) {
-          window.location.href = redirectURI;
-        } else {
+      // Same-origin only: `redirectURI` originates from the `?short_url=`
+      // query param, so an off-origin value here is a post-auth open redirect
+      // (see utils/common.ts redirectUser for the twin of this check).
+      if (redirectURI != null && redirectURI != "" && isSameOriginRedirect(redirectURI)) {
+        if (redirectURI.startsWith("/")) {
           router.push({ path: redirectURI });
+        } else {
+          window.location.href = redirectURI;
         }
       } else {
         router.push({ path: "/" });