Guard admin messages from leaking to frontend

apps/core/middleware.py

@@ -2,6 +2,8 @@ from __future__ import annotations
 
 import secrets
 
+from django.contrib.messages import get_messages
+
 from .consent import ConsentService
 
 
@@ -40,3 +42,25 @@ class SecurityHeadersMiddleware:
         )
         response["Permissions-Policy"] = "camera=(), microphone=(), geolocation=()"
         return response
+
+
+class AdminMessageGuardMiddleware:
+    ADMIN_PREFIXES = ("/cms/", "/django-admin/")
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        # The public site has no legitimate use of Django's shared flash queue.
+        # Drain any stale admin messages before frontend rendering can see them.
+        if not request.path.startswith(self.ADMIN_PREFIXES):
+            storage = get_messages(request)
+            list(storage)
+            storage._queued_messages = []
+            storage._loaded_data = []
+            for sub_storage in getattr(storage, "storages", []):
+                sub_storage._queued_messages = []
+                sub_storage._loaded_data = []
+                sub_storage.used = True
+            storage.used = True
+        return self.get_response(request)