The Popup Box plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 6.1.1. This is due to a flawed nonce implementation in the 'publish_unpublish_popupbox' function that verifies a self-created nonce rather than one submitted in the request. This makes it possible for unauthenticated attackers to change the publish status of popups via a forged request, granted they can trick a site administrator into performing an action such as clicking a link.