diff --git a/changedetectionio/notification/handler.py b/changedetectionio/notification/handler.py
index 951ed1e6..59a14710 100644
--- a/changedetectionio/notification/handler.py
+++ b/changedetectionio/notification/handler.py
@@ -382,14 +382,17 @@ def process_notification(n_object: NotificationContextData, datastore):
         n_object['llm_summary'] = _llm_change_summary or (n_object.get('_llm_result') or {}).get('summary', '')
         n_object['llm_intent'] = n_object.get('_llm_intent', '')
 
-    # Re #3529: diff content from text/plain pages may contain raw '<' chars that break HTML emails.
-    # Escape only the diff variables before Jinja2 renders them into the template, so the user's
-    # own HTML in the notification body (e.g. <a href="{{watch_url}}">) is never touched.
-    # Diff placemarkers (e.g. @removed_PLACEMARKER_OPEN) contain no HTML chars so they survive
-    # html_escape and are still replaced with <span> tags by apply_service_tweaks later.
-    watch_mime_type = n_object.get('watch_mime_type')
-    if (watch_mime_type and 'text/' in watch_mime_type.lower() and 'html' not in watch_mime_type.lower()
-            and 'html' in requested_output_format):
+    # Escape diff/snapshot variables before Jinja renders them into an HTML notification.
+    # GHSA-q8xq-qg4x-wphg: inscriptis decodes HTML entities when converting text/html
+    # pages to snapshot text, so a page that visibly displays "&lt;a href...&gt;" yields
+    # literal "<a href...>" in the snapshot — which would otherwise render as live
+    # markup in HTML emails / Telegram (parse_mode=html) / Discord embeds, letting a
+    # watched page inject phishing links into the operator's notification channel.
+    # Also covers #3529 — raw '<' chars from text/plain pages breaking HTML email layout.
+    # The operator's own template HTML (e.g. <a href="{{watch_url}}">) is outside the
+    # variable values so it stays untouched. Diff placemarkers contain no HTML chars,
+    # so they survive escape and are still replaced with <span> tags later.
+    if 'html' in requested_output_format:
         from markupsafe import escape as html_escape
         _page_content_keys = {'raw_diff', 'current_snapshot', 'prev_snapshot', 'triggered_text'}
         for key in [k for k in notification_parameters if k.startswith('diff') or k in _page_content_keys]:
diff --git a/changedetectionio/tests/test_notification.py b/changedetectionio/tests/test_notification.py
index bcdacd57..1d666793 100644
--- a/changedetectionio/tests/test_notification.py
+++ b/changedetectionio/tests/test_notification.py
@@ -638,9 +638,11 @@ def test_html_color_notifications(client, live_server, measure_memory_usage, dat
 
 def _test_custom_html_in_notification_body_not_escaped(client, datastore_path, content_type=None):
     """
-    #4121 - Custom HTML in the notification body (e.g. <a href="{{watch_url}}">) must NOT be
-    HTML-escaped regardless of the watched page's content-type. Only raw diff content from
-    text/plain pages needs escaping (to prevent raw '<' chars breaking HTML email rendering).
+    #4121 - The operator's own HTML in the notification body template (e.g.
+    <a href="{{watch_url}}">) must survive unescaped regardless of the watched page's
+    Content-Type. The escape pass in handler.py only touches the variable *values*
+    (diff/snapshot content from the page — see GHSA-q8xq-qg4x-wphg) — it leaves the
+    surrounding template HTML alone.
     """
     set_original_response(datastore_path=datastore_path)
 
@@ -693,10 +695,98 @@ def _test_custom_html_in_notification_body_not_escaped(client, datastore_path, c
 
 
 def test_plaintext_watch_custom_html_in_notification_body_not_escaped(client, live_server, measure_memory_usage, datastore_path):
-    # text/plain: diff content may contain raw '<' chars — those must be escaped, but NOT the user's template HTML
+    # Diff/snapshot values are escaped for HTML notifications (covered by
+    # test_html_watch_diff_content_escaped_in_html_notification). What this test
+    # locks in is that the *surrounding* template HTML is left alone in every case.
     _test_custom_html_in_notification_body_not_escaped(client, datastore_path, content_type="text/plain")
-    # text/html: HTML processor strips tags before diffing, no escaping needed, user's template HTML must be preserved
     _test_custom_html_in_notification_body_not_escaped(client, datastore_path, content_type="text/html")
-    # no MIME type (None): same as HTML case, user's template HTML must be preserved
     _test_custom_html_in_notification_body_not_escaped(client, datastore_path, content_type=None)
 
+
+def test_html_watch_diff_content_escaped_in_html_notification(client, live_server, measure_memory_usage, datastore_path):
+    """
+    GHSA-q8xq-qg4x-wphg — diff/snapshot content from the watched page must be
+    HTML-escaped before it is rendered into an HTML-format notification, regardless
+    of the watched page's Content-Type.
+
+    Inscriptis (used to convert text/html pages to snapshot text) decodes HTML
+    entities — so a page that visibly displays "&lt;a href=...&gt;" produces snapshot
+    text containing literal "<a href=...>". The previous gate at handler.py:391
+    only escaped when watch_mime_type matched 'text/' and not 'html', which let
+    that decoded markup through to HTML emails / Telegram (parse_mode=html) /
+    Discord embeds, where it renders as a real clickable link — i.e. an attacker
+    who controls a watched page can inject phishing links into the operator's
+    trusted notification channel.
+    """
+    from .util import write_test_file_and_sync
+
+    if os.path.isfile(os.path.join(datastore_path, "notification.txt")):
+        os.unlink(os.path.join(datastore_path, "notification.txt"))
+
+    # Baseline: an innocuous text/html page.
+    baseline_html = "<html><body><p>nothing to see here</p></body></html>"
+    write_test_file_and_sync(os.path.join(datastore_path, "endpoint-content.txt"), baseline_html)
+
+    test_notification_url = url_for('test_notification_endpoint', _external=True).replace('http://', 'post://')
+    # Pass content_type=text/html so the watch records 'text/html' as its content-type
+    # — this is the branch the previous gate skipped escaping for.
+    test_url = url_for('test_endpoint', _external=True, content_type='text/html')
+
+    # HTML-format notification body that embeds the snapshot directly. Operators do this
+    # when they want the full changed content in the alert (e.g. an email digest).
+    res = client.post(
+        url_for("settings.settings_page"),
+        data={
+            "application-fetch_backend": "html_requests",
+            "application-minutes_between_check": 180,
+            "application-notification_body": 'Watch had changes:\n{{current_snapshot}}',
+            "application-notification_format": "html",
+            "application-notification_urls": test_notification_url,
+            "application-notification_title": "Change detected",
+        },
+        follow_redirects=True
+    )
+    assert b'Settings updated' in res.data
+
+    res = client.post(
+        url_for("ui.ui_views.form_quick_watch_add"),
+        data={"url": test_url, "tags": ''},
+        follow_redirects=True
+    )
+    assert b"Watch added" in res.data
+
+    wait_for_all_checks(client)
+
+    # Now flip the page to something whose *visible* text contains entity-encoded
+    # angle brackets — exactly the pattern a forum / pastebin / code-sample site uses
+    # to display literal HTML on the page. Inscriptis will decode &lt;/&gt; back to
+    # literal < / > in the stored snapshot.
+    attacker_html = (
+        '<html><body><pre>'
+        '&lt;a href="https://attacker.example/payment"&gt;ACTION REQUIRED&lt;/a&gt;'
+        '&lt;img src="https://attacker.example/track" width="1" height="1"&gt;'
+        '</pre></body></html>'
+    )
+    write_test_file_and_sync(os.path.join(datastore_path, "endpoint-content.txt"), attacker_html)
+
+    res = client.get(url_for("ui.form_watch_checknow"), follow_redirects=True)
+    assert b'Queued 1 watch for rechecking.' in res.data
+
+    wait_for_all_checks(client)
+    wait_for_notification_endpoint_output(datastore_path=datastore_path)
+
+    with open(os.path.join(datastore_path, "notification.txt"), 'r') as f:
+        body = f.read()
+
+    # Sanity: the snapshot really did contain the decoded markup (otherwise the test
+    # would pass for the wrong reason). The escaped form must appear somewhere.
+    assert '&lt;a href=' in body or '&amp;lt;a href=' in body, \
+        f"Expected escaped attacker markup in notification body, got: {body!r}"
+
+    # The bug: a live <a href="https://attacker..."> ends up in the HTML notification.
+    assert '<a href="https://attacker.example/payment"' not in body, \
+        f"Diff content from text/html page was NOT escaped — phishing link reached HTML notification: {body!r}"
+    assert '<img src="https://attacker.example/track"' not in body, \
+        f"Diff content from text/html page was NOT escaped — tracking pixel reached HTML notification: {body!r}"
+
+    client.get(url_for("ui.form_delete", uuid="all"), follow_redirects=True)