The Quiz Maker WordPress plugin before 6.7.0.89 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
https://wpscan.com/vulnerability/1ff8ea2b-6513-4d5c-b7ea-9ab39c9ea9c6/