The WatchTowerHQ plugin for WordPress is vulnerable to authentication bypass in versions up to, and including, 3.9.6. This is due to the 'watchtower_ota_token' default value is empty, and the not empty check is missing in the 'Password_Less_Access::login' function. This makes it possible for unauthenticated attackers to log in to the WatchTowerHQ client administrator user.