QuickCMS is vulnerable to multiple Stored XSS in language editor functionality (languages). Malicious attacker with admin privileges can inject arbitrary HTML and JS into website, which will be rendered/executed on every page. By default admin user is not able to add JavaScript into the website.
The vendor was notified early about this vulnerability, but didn't respond with the details of vulnerability or vulnerable version range. Only version 6.8 was tested and confirmed as vulnerable, other versions were not tested and might also be vulnerable.