WWBN AVideo is an open source video platform. In versions 26.0 and prior, the AVideo endpoint objects/emailAllUsers.json.php allows administrators to send HTML emails to every registered user on the platform. While the endpoint verifies admin session status, it does not validate a CSRF token. Because AVideo sets SameSite=None on session cookies, a cross-origin POST request from an attacker-controlled page will include the admin's session cookie automatically. An attacker who lures an admin to a malicious page can send an arbitrary HTML email to every user on the platform, appearing to originate from the instance's legitimate SMTP address. At time of publication, there are no publicly available patches.