Mattermost doesn't validate CSRF tokens on an authentication endpoint

Mattermost versions 10.11.x = 10.11.12, 11.5.x = 11.5.0, 11.4.x = 11.4.2, 11.3.x = 11.3.2 fail to validate CSRF tokens on an authentication endpoint which allows an attacker to update a user's authentication method via a CSRF attack by tricking a user into visiting a malicious page. Mattermost...