Profile Builder Pro <= 3.14.5 - Unauthenticated PHP Object Injection

The Profile Builder Pro plugin for WordPress is vulnerable to PHP Object Injection in all versions up to and including 3.14.5. This is due to the use of PHP's maybe_unserialize() function on the attacker-controlled 'args' POST parameter within the wppb_request_users_pins_action_callback() AJAX handler, which lacked any nonce verification, type checking, or input validation before deserialization. Because the handler was registered with both wp_ajax_ and wp_ajax_nopriv_ hooks, it was reachable by completely unauthenticated users. This makes it possible for unauthenticated attackers to inject arbitrary PHP objects into application memory.