This indicates an attack attempt against a Cross-Site Scripting vulnerability in Nullsoft ShoutcastServer.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when parsing malicious URI. A remote attacker may be able to exploit this to execute script arbitrary code within the context of the application, via a crafted HTTP request.
Nullsoft ShoutcastServer 1.9.7
System Compromise: Remote attackers can execute arbitrary script code within the context of the targeted user.
Currently we are unaware of any vendor supplied patch for this issue.