PYSEC-2026-3598

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:

<img width="690" height="383" alt="image" src="https://github.com/user-attachments/assets/70208661-a0db-4457-9984-119056ca3daf" />

7. 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:

<img width="1642" height="577" alt="image" src="https://github.com/user-attachments/assets/6639d982-a156-4e8b-861e-587d86d9b152" />

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

<img width="400" alt="app aikido dev_ai-pentests_projects_116389_assessments_019d67d4-81c8-7dd2-bb9e-0a4a774b2c78_issues_sidebarIssue=20440423 (4)" src="https://github.com/user-attachments/assets/8415553a-9f1e-4f73-929c-aa0d18a101ca" />