Mattermost versions <11.0 fail to properly enforce the "Allow users to view archived channels" setting which allows regular users to access archived channel content and files via the "Open in Channel" functionality from followed threads
Mattermost versions <11 fail to enforce multi-factor authentication on WebSocket connections which allows unauthenticated users to access sensitive information via WebSocket events
Mattermost versions <11 fail to properly restrict access to archived channel search API which allows guest users to discover archived public channels via the `/api/v4/teams/{team_id}/channels/search_archived` endpoint
Mattermost versions 10.6.x <= 10.6.1, 10.5.x <= 10.5.2, 10.4.x <= 10.4.4, 9.11.x <= 9.11.11 fail to check the correct permissions which allows authenticated users who only have permission to invite non-guest users to a team to add guest users to that team via the API to add a single user to a team.
Mattermost versions 10.5.x <= 10.5.1, 10.4.x <= 10.4.3, 9.11.x <= 9.11.9 fail to properly enforce the 'Allow users to view/update archived channels' System Console setting, which allows authenticated users to view members and member information of archived channels even when this setting is disabled.
Mattermost Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison.
Mattermost versions 10.5.x <= 10.5.1, 10.4.x <= 10.4.3, 9.11.x <= 9.11.9 fail to check the "Allow Users to View Archived Channels" configuration when fetching channel metadata of a post from archived channels, which allows authenticated users to access such information when a channel is archived.
Mattermost versions 10.5.x <= 10.5.1, 10.4.x <= 10.4.3, 9.11.x <= 9.11.9 fail to prevent Wrangler posts from triggering AI responses. This vulnerability allows users without access to the AI bot to activate it by attaching the activate_ai override property to a post via the Wrangler plugin, provided both the AI and Wrangler plugins are enabled.
Mattermost versions 10.5.x <= 10.5.1, 10.4.x <= 10.4.3, 9.11.x <= 9.11.9 fail to invalidate the cache when a user account is converted to a bot which allows an attacker to login to the bot exactly one time via normal credentials.