The Insert Headers And Footers plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 3.1.1. This is due to missing or incorrect nonce validation on the 'custom_plugin_set_option' function. This makes it possible for unauthenticated attackers to update arbitrary options on the WordPress site via a forged request granted they can trick a site administrator into performing an action such as clicking on a link. This can be leveraged to update the default role for registration to administrator and enable user registration for attackers to gain administrative user access to a vulnerable site. The 'WPBRIGADE_SDK__DEV_MODE' constant must be set to 'true' to exploit the vulnerability.