diff --git a/backend/windmill-api-integration-tests/tests/workspace_dependencies.rs b/backend/windmill-api-integration-tests/tests/workspace_dependencies.rs
new file mode 100644
index 0000000000..0132a98a61
--- /dev/null
+++ b/backend/windmill-api-integration-tests/tests/workspace_dependencies.rs
@@ -0,0 +1,57 @@
+use serde_json::json;
+use sqlx::{Pool, Postgres};
+
+#[allow(unused_imports)]
+use windmill_test_utils::*;
+
+/// An admin of one workspace must not be able to write dependency files into another
+/// by naming it in the request body.
+#[sqlx::test(migrations = "../migrations", fixtures("base"))]
+async fn test_create_rejects_body_workspace_other_than_path(
+    db: Pool<Postgres>,
+) -> anyhow::Result<()> {
+    initialize_tracing().await;
+
+    // test-user-2 is a plain user of test-workspace and an admin of its own workspace.
+    sqlx::query("INSERT INTO workspace (id, name, owner) VALUES ('own-workspace', 'own-workspace', 'test-user-2')")
+        .execute(&db)
+        .await?;
+    sqlx::query("INSERT INTO usr (workspace_id, email, username, is_admin, role) VALUES ('own-workspace', 'test2@windmill.dev', 'test-user-2', true, 'Admin')")
+        .execute(&db)
+        .await?;
+
+    let (_client, port, _server) = init_client(db.clone()).await;
+
+    let resp = reqwest::Client::new()
+        .post(format!(
+            "http://localhost:{port}/api/w/own-workspace/workspace_dependencies/create"
+        ))
+        .header("Authorization", "Bearer SECRET_TOKEN_2")
+        .json(&json!({
+            "workspace_id": "test-workspace",
+            "language": "python3",
+            "content": "requests==2.28.0"
+        }))
+        .send()
+        .await?;
+    let status = resp.status().as_u16();
+    let body = resp.text().await?;
+    assert_eq!(
+        status, 400,
+        "expected the mismatched body to be rejected, got {body}"
+    );
+    assert!(
+        body.contains("does not match"),
+        "expected the workspace mismatch rejection, got {body}"
+    );
+
+    let written: i64 = sqlx::query_scalar("SELECT count(*) FROM workspace_dependencies")
+        .fetch_one(&db)
+        .await?;
+    assert_eq!(
+        written, 0,
+        "no dependency file may be written in either workspace"
+    );
+
+    Ok(())
+}
diff --git a/backend/windmill-api/openapi.yaml b/backend/windmill-api/openapi.yaml
index 5f2bd9e66c..c308559c0b 100644
--- a/backend/windmill-api/openapi.yaml
+++ b/backend/windmill-api/openapi.yaml
@@ -10872,6 +10872,8 @@ paths:
             text/plain:
               schema:
                 type: string
+        "400":
+          description: the body's workspace_id does not match the workspace in the path
 
   /w/{workspace}/workspace_dependencies/archive/{language}:
     post:
@@ -29504,6 +29506,7 @@ components:
       properties:
         workspace_id:
           type: string
+          description: must equal the workspace in the request path
         language:
           $ref: "#/components/schemas/ScriptLang"
         name:
diff --git a/backend/windmill-api/src/workspace_dependencies.rs b/backend/windmill-api/src/workspace_dependencies.rs
index 194cc1f0d5..170006f44a 100644
--- a/backend/windmill-api/src/workspace_dependencies.rs
+++ b/backend/windmill-api/src/workspace_dependencies.rs
@@ -34,13 +34,20 @@ async fn create(
     authed: ApiAuthed,
     // Extension(user_db): Extension<UserDB>,
     Extension(db): Extension<DB>,
+    Path(w_id): Path<String>,
     Json(nwd): Json<NewWorkspaceDependencies>,
 ) -> error::Result<(StatusCode, String)> {
-    tracing::info!(workspace_id = %nwd.workspace_id, name = ?nwd.name, language = ?nwd.language, "create workspace dependencies");
+    tracing::info!(workspace_id = %w_id, name = ?nwd.name, language = ?nwd.language, "create workspace dependencies");
     require_admin(authed.is_admin, &authed.username)?;
+    // `require_admin` vouches for the path workspace only; the body must not target another.
+    if nwd.workspace_id != w_id {
+        return Err(error::Error::BadRequest(format!(
+            "workspace_id `{}` in the request body does not match the workspace `{}` in the path",
+            nwd.workspace_id, w_id
+        )));
+    }
 
     let dep_path = WorkspaceDependencies::to_path(&nwd.name, nwd.language)?;
-    let w_id = nwd.workspace_id.clone();
     let email = authed.email.clone();
     let username = authed.username.clone();
 
diff --git a/backend/windmill-dep-map/src/workspace_dependencies.rs b/backend/windmill-dep-map/src/workspace_dependencies.rs
index 03db1405e5..f4dd404133 100644
--- a/backend/windmill-dep-map/src/workspace_dependencies.rs
+++ b/backend/windmill-dep-map/src/workspace_dependencies.rs
@@ -11,6 +11,8 @@ use crate::{
 
 #[derive(sqlx::FromRow, Clone, Serialize, Deserialize, Hash, Debug)]
 pub struct NewWorkspaceDependencies {
+    /// Trusted as-is by `create`: a caller deserializing this from a request must first check it
+    /// against the workspace the caller is authorized in.
     pub workspace_id: String,
     pub language: ScriptLang,
     pub name: Option<String>,