The HD Quiz plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions 2.2.0 to 2.2.1. This is due to missing or incorrect nonce validation on the hdq_validate_nonce function. This makes it possible for unauthenticated attackers to delete or modify quizzes and questions, create new quizzes, and change plugin settings via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.