Juho Nurminen

Mattermost version 8.1.x before 8.1.9 fails to sanitize data associated with permalinks when a plugin updates an ephemeral post, allowing an authenticated attacker who can control the ephemeral post update to access individual posts' contents in channels

Information disclosure in linked message previews

Unrestricted navigation due to unvalidated mattermost server redirection

Collapsed Reply Threads APIs leak message contents from private channels

Playbooks lets you edit arbitrary posts

Ephemeral messages return private channel contents in permalink previews

Stack exhaustion in PreparePostForClientWithEmbedsAndImages

Path traversal in GitHub plugin's code preview feature

WebSockets accept connections from HTTPS origin

Private channel names leaked with Ctrl+K when ElasticSearch is enabled