The WowOptin: Next-Gen Popup Maker WordPress plugin before 1.4.38 does not have proper authorization on a REST endpoint, allowing unauthenticated users to disable all of the site's opt-in forms and insert new template-based opt-in rows into the database.
https://wpscan.com/vulnerability/3a06d27a-9405-4cf2-9087-554018d31884/