CVE-2026-4265 Guest user can upload files without permission across teams

Mattermost versions 11.3.x = 11.3.0, 11.2.x = 11.2.2, 10.11.x = 10.11.10 fail to validate team-specific uploadfile permissions which allows a guest user to post files in channels where they lack uploadfile permission via uploading files in a team where they have permission and reusing the file...