This indicates an attempt at exploiting a Cross Site Scripting Vulnerability in Cpanel. Cpanel is a next web hosting control panel system. There exists multiple Cross Site Scripting Vulnerabilities (XSS) which could lead to the execution of arbitrary HTML or script code in the users browser. These issues exist because the application does not properly validate user-supplied URI input.
Compromise of the affected system.
Apply appropriate patch from the vendor or Upgrade to non-vulnerable version if available.