Insufficient verification of data authenticity in Open WebUI - #VU159308
Published: November 4, 2026
Vulnerability details
The vulnerability allows a remote user to spoof a trusted channel webhook's identity in displayed messages.
The vulnerability exists due to insufficient verification of client-supplied metadata in the channel message post and edit endpoints in backend/open_webui/routers/channels.py when processing message submissions and edits. A remote user can submit messages containing metadata that identifies an existing channel webhook, using write access to the channel, to make their messages appear under the webhook's name and role in channel and pinned message lists.
Exploitation requires channels to be enabled through ENABLE_CHANNELS, which is disabled by default, and at least one webhook in the channel. The stored message author remains the submitting user's account; exploitation does not grant access to the webhook token or allow modification of the webhook's actual messages.