Input validation vulnerability in Sign-up Sheets 2.3.3

A plugin called “Sign-up Sheets” for WordPress has a security issue called Cross-Site Request Forgery. This means that anyone, even without an account, can make the site do something without permission. All versions of the plugin up to 2.3.3 are affected. This happens because the plugin doesn’t check for a special code that ensures the action is authorized. Attackers can take advantage of this by tricking a site administrator into clicking on a link.