Mattermost fails to properly validate markdown, allowing an attacker to crash the server via a specially crafted markdown input.

Mattermost fails to disable public Boards after the "Enable Publicly-Shared Boards" configuration option is disabled, resulting in previously-shared public Boards to remain accessible.

Mattermost fails to verify channel membership when linking a board to a channel allowing a low-privileged authenticated user to link a Board to a private channel they don't have access to,

Mattermost fails to properly restrict requests to localhost/intranet during the interactive dialog, which could allow an attacker to perform a limited blind SSRF.