docs: note CSRF POST and DOM XSS rules in AGENTS.md (#2684)

Document that mutating dynamic-analysis actions must be POST with a CSRF
token, and that template auto-escaping does not protect innerHTML sinks.

Co-authored-by: Cursor Agent <[email protected]>

AGENTS.md

@@ -142,7 +142,9 @@ def my_view(request, api=False):
 Django's template engine escapes variables by default. Do **not** use `{% autoescape off %}`
 or the `|safe` filter on any value derived from scan data, manifests, or user input.
 When rendering user-controlled strings outside of templates (e.g., in a JSON response
-built by hand), use `django.utils.html.escape()` explicitly.
+built by hand), use `django.utils.html.escape()` explicitly. Template auto-escaping
+does not protect JavaScript DOM sinks: never assign scan, task, or user-derived
+strings to `innerHTML`; use `textContent` (see `templates/general/tasks.html`).
 
 ### ORM — No Raw SQL
 
@@ -163,7 +165,9 @@ RecentScansDB.objects.raw(f'SELECT * FROM ... WHERE MD5 = "{checksum}"')
 Django's `CsrfViewMiddleware` is enabled globally. Do not use `@csrf_exempt` on any
 view that modifies state. API endpoints that accept an `X-Csrftoken` header or use
 token-based auth are the only legitimate exception, and that pattern is already
-established in the existing API views.
+established in the existing API views. Mutating actions (including dynamic-analysis
+start/stop/stream) must be POST with a CSRF token, not GET. Split GET-render from
+POST-stream when a page both renders and then streams (e.g. logcat).
 
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