XSS vulnerability in WebPress

Vulnerability ID: HTB22481
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_webpress_3.html
Product: WebPress
Vendor: YWP ( http://www.goywp.com/ )
Vulnerable Version: Current at 01.07.2010 and Probably Prior Versions
Vendor Notification: 01 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 "admin_page_accounts_users_action.php" script to properly sanitize user-supplied input in "id_num_mod" variable. 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/path/_system/accounts/users/_pages/admin_page_accounts_users_action.php?id_num_mod=xxx%3Cscript%3Ealert%28document.cookie%29%3C/script%3E&submit_action=Edit