The Countdown, Coming Soon, Maintenance – Countdown & Clock plugin for WordPress is vulnerable to unauthorized access due to a missing capability check on the conditionsRow and switchCountdown functions in all versions up to, and including, 2.7.8. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject PHP Objects and modify the status of countdowns.
https://plugins.trac.wordpress.org/changeset/3097588/
https://plugins.trac.wordpress.org/changeset/3096150/
https://plugins.trac.wordpress.org/browser/countdown-builder/trunk/classes/Ajax.php#L92
https://plugins.trac.wordpress.org/browser/countdown-builder/trunk/classes/Ajax.php#L51