The WatchTowerHQ plugin for WordPress is vulnerable to authentication bypass in versions up to, and including, 3.10.1. 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.
https://plugins.trac.wordpress.org/changeset/3177064/watchtowerhq#file2
https://plugins.trac.wordpress.org/browser/watchtowerhq/tags/3.9.6/src/Password_Less_Access.php#L56