The Parallels Plesk Panel software package is a commercial web hosting automation program. Parallels Plesk Single Sign-On (SSO) technology make it easy for customers to use and manage applications, and reduce the administrative costs of password management for hosting providers. Parallels Plesk Single Sign-On (SSO) implementation was found vulnerable to XXE (XML External Entity) and XSS (Cross-site scripting) vulnerabilities.
To disable SSO-mode in Parallels Plesk Panel:
~# /usr/local/psa/bin/sso --disable