XSS vulnerability in allinta CMS

Vulnerability ID: HTB22528
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_allinta_cms.html
Product: Allinta CMS
Vendor: Allinta ( http://www.allinta.com/ )
Vulnerable Version: Current at 22.07.2010 and Probably Prior Versions
Vendor Notification: 26 July 2010
Vulnerability Type: XSS (Cross Site Scripting)
Status: Not Fixed, Vendor Alerted, Awaiting Vendor Response
Risk level: Medium
Credit: High-Tech Bridge SA - Ethical Hacking & Penetration Testing (http://www.htbridge.ch/)

Vulnerability Details:
User can execute arbitrary JavaScript code within the vulnerable application.

The vulnerability exists due to failure in the "/languageselect.asp" script to properly sanitize user-supplied input in multiple variables. Successful exploitation of this vulnerability could result in a compromise of the application, theft of cookie-based authentication credentials, disclosure or modification of sensitive data.

An attacker can use browser to exploit this vulnerability. The following PoC is available:

http://host/languageselect.asp?lang_URL=Default.asp%3Flang%3D&ss=x%22%3E%3Cscript%3Ealert%28document.cookie%29%3C/script%3E&img=1
http://host/languageselect.asp?lang_URL=Default.asp%27};alert%28document.cookie%29;{a=%27%3Flang%3D&ss=x&img=1