source: https://www.securityfocus.com/bid/21067/info

Plesk is prone to multiple HTML-injection vulnerabilities because it fails to sufficiently sanitize user-supplied input data.

Exploiting these issues may allow an attacker to execute HTML and script code in the context of the affected site, to steal cookie-based authentication credentials, or to control how the site is rendered to the user; other attacks are also possible.

Plesk 8.0.1 and prior versions are vulnerable.

http://www.example.com:8443/login_up.php3/>"><ScRiPt>alert(15031988)</ScRiPt>