This indicates an attack attempt against a Cross-Site Scripting vulnerability in Cisco Wireless Lan Controller.
The vulnerability is due to the user input filters failing to properly sanitize the parameters value that is passed to "web_auth_custom.html". A remote attacker may be able to exploit this to execute arbitrary script code within the context of the application, via a crafted HTTP request.
Cisco Wireless Lan Controller 188.8.131.52
System Compromise: Remote attackers can execute arbitrary script code in the context of the application.
Currently we are unaware of any vendor supplied patch for this issue.