CVE-2026-9597 Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint

Mattermost versions 11.7.x = 11.7.2, 11.6.x = 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation...