The Popup Manager WordPress plugin through 1.6.6 does not have authorisation and CSRF check when creating/updating popups, and is missing sanitisation as well as escaping, which could allow unauthenticated attackers to create arbitrary popups and add Stored XSS payloads as well
https://wpscan.com/vulnerability/7862084a-2821-4ef1-8d01-c9c8b3f28b05