Open WebUI's Mass Assignment via Pydantic extra='allow' Allows Creating Folders in Other Users' Accounts

# Mass Assignment via Pydantic extra='allow' Allows Creating Folders in Other Users' Accounts ## Affected Component Folder creation endpoint and form model: - `backend/open_webui/models/folders.py` (lines 72-77, `FolderForm` with `extra='allow'`) - `backend/open_webui/models/folders.py` (lines 95-106, `insert_new_folder` dict construction) - `backend/open_webui/routers/folders.py` (line 119, `create_folder` endpoint) ## Affected Versions Current main branch (commit `6fdd19bf1`) and likely all versions since `FolderForm` adopted `extra='allow'`. ## Description `FolderForm` uses `model_config = ConfigDict(extra='allow')`, which permits arbitrary fields to pass through Pydantic validation and be included in `model_dump(exclude_unset=True)`. In `insert_new_folder`, the server-assigned `user_id` is placed at the start of the dict and then overwritten by the spread of form data: ```python # models/folders.py:95-106 folder = FolderModel( **{ 'id': id, # server 'user_id': user_id, # server — overwritten below **(form_data.model_dump(exclude_unset=True) or {}), # user-controlled (extra='allow') 'parent_id': parent_id, 'created_at': int(time.time()), 'updated_at': int(time.time()), } ) ``` Because `FolderModel` declares `user_id: str` as a real field (not just a form extra), any attacker-supplied `user_id` in the POST body is accepted by the model and persisted on the `Folder` row. ## Attack Scenario 1. Attacker discovers a victim's user ID. User UUIDs commonly leak via the user search endpoint (`GET /api/v1/users/search`, intentionally accessible to verified users for sharing UI), shared chat metadata, or channel member lists. 2. Attacker sends: ``` POST /api/v1/folders/ { "name": "Important: Click here", "user_id": "<victim_user_id>", "meta": {"icon": "warning"}, "data": {...} } ``` 3. Pydantic accepts the extra `user_id` field (allowed by `extra='allow'`). 4. `insert_new_folder` spreads the form data over the server-set `'user_id': user_id`, overwriting it with the attacker's value. 5. The `Folder` row is persisted with `user_id = <victim_user_id>`. 6. The victim sees the attacker-planted folder in their UI on next load because `GET /api/v1/folders/` filters by the viewer's own `user_id`. The attacker can repeat this to plant multiple folders, use crafted `name` values for phishing ("Click here to recover account" / "Security alert"), and abuse the `meta` and `data` fields to add visual elements that further mimic legitimate content. ## Impact - Unauthorized write into victim's folder tree - Phishing surface: attacker-controlled `name`, `meta`, and `data` render in the victim's UI in a trusted context - DoS / spam: attacker can flood a victim with arbitrary folders; victim must manually delete each one - Attacker cannot read the folder back — all read paths filter by the caller's own `user_id` — so confidentiality is preserved, but integrity and trust are compromised ## Preconditions - Attacker must have an authenticated account with `features.folders` permission (default for all users) - Attacker must know or guess the victim's user UUID (obtainable through various non-sensitive endpoints)