Mattermost fails to properly sanitize the request to /api/v4/redirect_location allowing an attacker, sending a specially crafted request to /api/v4/redirect_location, to fill up the memory due to caching large items.
Mattermost fails to normalize UTF confusable characters when determining if a preview should be generated for a hyperlink, allowing an attacker to trigger link preview on a disallowed domain using a specially crafted link.
Mattermost fails to check the "Show Full Name" setting when rendering the result for the /plugins/focalboard/api/v2/users API call, allowing an attacker to learn the full name of a board owner.
A missing permissions check in the /plugins/playbooks/api/v0/runs API in Mattermost allows an attacker to list and view playbooks belonging to a team they are not a member of.
A missing permissions check in Mattermost Playbooks in Mattermost allows an attacker to modify a playbook via the /plugins/playbooks/api/v0/playbooks/[playbookID] API.