The plugin did not sanitise or escape its result_id parameter when displaying an existing quiz result page, leading to a reflected Cross-Site Scripting issue. This could allow for privilege escalation by inducing a logged in admin to open a malicious link
Proof of Concept
1) Create a quiz.
2) In the "results pages" tab add the %RESULT_LINK% template to display a link to your result when finishing the quiz.
3) Publish your quiz or click the preview button.
4) Take the quiz and copy your results link:
5) Append <"><script>alert(document.domain)</script> to the result_id and reload the page.
Note (WPScanTeam): As the affected function is hooked to the wp_head action, only the result_id is required to perform the attack, no need to go to the quiz page, ie https://example.com/?result_id=1597bc5d9f9a2c9659152522904df0c0%3C%22%3E%3Cscript%3Ealert(document.domain)%3C/script%3E