Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.5, 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. 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. This vulnerability is fixed in 0.9.5.