The CMP WordPress plugin before 4.1.18 does not perform authorization checks on one of its AJAX actions and relies on a nonce that is skipped for certain (and exposed to anonymous visitors on others), allowing unauthenticated attackers to disable the site's maintenance/coming-soon mode under a non-default countdown configuration.
https://wpscan.com/vulnerability/096f11ce-060a-403a-8af0-ae2ee7676318/