From 0f1fc2bb5dfa1bd53308567e65125613a774387d Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Mon, 19 Oct 2026 01:15:39 +0200
Subject: [PATCH] fix: sanitise imported and synced HTML templates before the
 composer previews them

---
 components/templates/placeholder-fill-modal.tsx |  4 +++-
 lib/__tests__/template-utils.test.ts            | 14 ++++++++++++++
 lib/template-utils.ts                           | 15 +++++++++++++--
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/components/templates/placeholder-fill-modal.tsx b/components/templates/placeholder-fill-modal.tsx
index b274b1de1..e66ad426c 100644
--- a/components/templates/placeholder-fill-modal.tsx
+++ b/components/templates/placeholder-fill-modal.tsx
@@ -7,6 +7,7 @@ import { cn } from '@/lib/utils';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { substitutePlaceholders, isBuiltInPlaceholder } from '@/lib/template-utils';
+import { sanitizeEmailHtml } from '@/lib/email-sanitization';
 import { useFocusTrap } from '@/hooks/use-focus-trap';
 import type { EmailTemplate } from '@/lib/template-types';
 
@@ -94,7 +95,8 @@ export function PlaceholderFillModal({
             <div className="mt-4 pt-4 border-t border-border">
               <p className="text-xs font-medium text-muted-foreground mb-2">{t('preview')}</p>
               <div className="text-sm text-foreground whitespace-pre-wrap p-3 rounded-md bg-muted/50 border border-border max-h-32 overflow-y-auto">
-                {template.isHTML ? <div dangerouslySetInnerHTML={{ __html: preview }}></div> : preview}
+                {/* The body may come from an imported file or a synced blob; it is markup in the app document here. */}
+                {template.isHTML ? <div dangerouslySetInnerHTML={{ __html: sanitizeEmailHtml(preview) }}></div> : preview}
               </div>
             </div>
           )}
diff --git a/lib/__tests__/template-utils.test.ts b/lib/__tests__/template-utils.test.ts
index 16404ade4..f33d01288 100644
--- a/lib/__tests__/template-utils.test.ts
+++ b/lib/__tests__/template-utils.test.ts
@@ -221,6 +221,20 @@ describe('importTemplates', () => {
     expect(result.templates[0].id).not.toBe('test-id');
   });
 
+  it('strips script and event handlers from an imported HTML body', () => {
+    // The body reaches the composer's placeholder preview as markup in the
+    // app document; it used to be kept exactly as the file had it.
+    const json = JSON.stringify({
+      type: 'webmail-templates',
+      version: 1,
+      templates: [{ name: 'Evil', isHTML: true, body: '<p>Hi {{name}}</p><img src=x onerror="alert(1)"><script>alert(2)</script>' }],
+    });
+    const body = importTemplates(json).templates[0].body;
+    expect(body).toContain('Hi {{name}}');
+    expect(body).not.toContain('onerror');
+    expect(body).not.toContain('<script');
+  });
+
   it('returns error for invalid JSON', () => {
     const result = importTemplates('not json');
     expect(result.templates).toHaveLength(0);
diff --git a/lib/template-utils.ts b/lib/template-utils.ts
index f509c488e..b6a4bf538 100644
--- a/lib/template-utils.ts
+++ b/lib/template-utils.ts
@@ -1,4 +1,5 @@
 import DOMPurify from 'dompurify';
+import { sanitizeEmailHtml } from './email-sanitization';
 import type { EmailTemplate } from './template-types';
 import { BUILT_IN_PLACEHOLDERS } from './template-types';
 import { generateUUID } from './utils';
@@ -138,6 +139,16 @@ function sanitizeText(value: unknown): string {
   return DOMPurify.sanitize(String(value || ''), STRIP_HTML_CONFIG);
 }
 
+/**
+ * An HTML template body from outside the app (a templates file, a synced
+ * settings blob written by another client) as the store may hold it. Bodies
+ * the plugin API creates are sanitised at creation; these were kept raw and
+ * reached the composer's placeholder preview as markup in the app document.
+ */
+function sanitizeTemplateHtml(value: unknown): string {
+  return sanitizeEmailHtml(String(value || ''));
+}
+
 interface ExportData {
   version: 1;
   type: 'webmail-templates';
@@ -199,7 +210,7 @@ export function parseSyncedTemplates(value: unknown): EmailTemplate[] | null {
       id: t.id,
       name: sanitizeText(t.name),
       subject: sanitizeText(t.subject),
-      body: t.isHTML ? String(t.body || '') : sanitizeText(t.body),
+      body: t.isHTML ? sanitizeTemplateHtml(t.body) : sanitizeText(t.body),
       isHTML: Boolean(t.isHTML),
       category: sanitizeText(t.category),
       defaultRecipients: recipients && typeof recipients === 'object'
@@ -277,7 +288,7 @@ export function importTemplates(json: string): ImportResult {
       id: generateUUID(),
       name: sanitizeText(t.name),
       subject: sanitizeText(t.subject),
-      body: t.isHTML ? String(t.body || '') : sanitizeText(t.body),
+      body: t.isHTML ? sanitizeTemplateHtml(t.body) : sanitizeText(t.body),
       isHTML: Boolean(t.isHTML),
       category: sanitizeText(t.category),
       defaultRecipients: recipients && typeof recipients === 'object'