CVE-2026-59222: Open WebUI: /api/v1/channels/{id}/members exposes full user model including sensitive credentials

Summary

The channel members endpoint serializes and returns full user models for channel participants, including settings objects. A normal user in a DM can retrieve admin-only sensitive configuration such as webhook URLs and tool server key material (settings.ui.toolServers[].key), which is not available via standard user info APIs.

Details

The endpoint GET /api/v1/channels/{id}/members returns the full serialized user model for every member in the channel. In both the DM and non-DM code paths, the handler constructs the response with [UserModelResponse(**user.model_dump(), is_active=...)] and returns it as the users list. Because UserModel (models/users.py) includes a settings object (UserSettings) and arbitrary UI configuration (settings.ui), the endpoint exposes other users' sensitive configuration to any channel participant.

Practically, a regular user who participates in a DM or group can call /api/v1/channels/{id}/members and receive other members' settings, including admin-only details such as webhook notification URLs and tool server configuration, including credential fields like settings.ui.toolServers[].key. These values are not returned by the normal user profile endpoints (e.g., /api/v1/users/{user_id}/info).

PoC

1. Start a local Open WebUI instance
2. Log in as admin and in the Admin Panel, go to Settings -> General and check *Channels (Beta)*, then press Save.
3. Create a low-privilege user in the Users tab
4. Click on the admin's profile bottom left, Settings and Integrations. Then click the + after *Manage Tool Servers* to add some tool server with a secret Bearer token (eg. KEY)
5. Log in as the attacker with the low-privilege account and create a new Direct Message channel with the admin user:

1. After creating, open DevTools with F12 and go to the Network tab. Then in the DM UI click on the *Users* icon top right to see the members. In the network tab, this should have triggered a /api/v1/channels/{id}/members request which responds with the settings key including toolServers and key values:

The attacker has now leaked the admin's bearer token for the toolserver they configured.

Impact

Conditions for exploit: channels are enabled and an attacker has a low-privilege account.

Webhook URLs and tool server configurations (including bearer keys) can be exfiltrated from any user.

Original Agent Report