perf: redirect default model profile image to canonical static URL (#24015)

- Return 302 to /static/favicon.png instead of streaming the same PNG per
  model id so browsers can cache one asset for default avatars.
- Validate stored /static/ paths with decode, normpath, and /static
  prefix checks; invalid paths fall back to favicon.

Made-with: Cursor

backend/open_webui/routers/models.py

@@ -4,6 +4,8 @@ import base64
 import json
 import asyncio
 import logging
+import posixpath
+from urllib.parse import unquote
 
 from open_webui.models.groups import Groups
 from open_webui.models.models import (
@@ -29,12 +31,12 @@ from fastapi import (
     status,
     Response,
 )
-from fastapi.responses import FileResponse, StreamingResponse
+from fastapi.responses import RedirectResponse, StreamingResponse
 
 
 from open_webui.utils.auth import get_admin_user, get_verified_user
 from open_webui.utils.access_control import has_permission, filter_allowed_access_grants
-from open_webui.config import BYPASS_ADMIN_ACCESS_CONTROL, STATIC_DIR
+from open_webui.config import BYPASS_ADMIN_ACCESS_CONTROL
 from open_webui.internal.db import get_async_session
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -43,6 +45,34 @@ log = logging.getLogger(__name__)
 router = APIRouter()
 
 
+def _safe_static_redirect_path(url: str) -> Optional[str]:
+    """
+    If url is a same-origin static asset path, return a normalized path safe for
+    RedirectResponse Location. Otherwise None (caller should fall back to default).
+    Rejects traversal (..), encoded dots, query/fragment, and non-/static targets.
+    """
+    if not url or not isinstance(url, str):
+        return None
+    path = url.split('?', 1)[0].split('#', 1)[0].strip()
+    for _ in range(2):
+        decoded = unquote(path)
+        if decoded == path:
+            break
+        path = decoded
+    if '\x00' in path or '\\' in path:
+        return None
+    if not path.startswith('/'):
+        return None
+    normalized = posixpath.normpath(path)
+    if normalized in ('.', '/'):
+        return None
+    if not (normalized == '/static' or normalized.startswith('/static/')):
+        return None
+    if normalized == '/static':
+        return '/static/'
+    return normalized
+
+
 def is_valid_model_id(model_id: str) -> bool:
     return model_id and len(model_id) <= 256
 
@@ -465,10 +495,25 @@ async def get_model_profile_image(
                     )
                 except Exception as e:
                     pass
+            else:
+                safe_static = _safe_static_redirect_path(model.meta.profile_image_url)
+                if safe_static:
+                    return RedirectResponse(
+                        url=safe_static,
+                        status_code=status.HTTP_302_FOUND,
+                    )
 
-        return FileResponse(f'{STATIC_DIR}/favicon.png')
+        # Canonical URL so browsers cache one asset for all default model avatars
+        # (distinct /profile/image?id=... URLs would otherwise re-download the same bytes).
+        return RedirectResponse(
+            url='/static/favicon.png',
+            status_code=status.HTTP_302_FOUND,
+        )
     else:
-        return FileResponse(f'{STATIC_DIR}/favicon.png')
+        return RedirectResponse(
+            url='/static/favicon.png',
+            status_code=status.HTTP_302_FOUND,
+        )
 
 
 ############################