PhpList Subber <= 1.1 - Cross-Site Request Forgery

The PhpList Subber plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 1.1. This is due to missing or incorrect nonce validation on the bulk_action_handler function. This makes it possible for unauthenticated attackers to trigger bulk synchronization of subscription forms via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.