Vulnerability ID: HTB22672
Reference: http://www.htbridge.ch/advisory/xss_in_textpattern_cms.html
Product: Textpattern CMS 
Vendor: Team Textpattern  ( http://textpattern.com/ ) 
Vulnerable Version: 4.2.0
Vendor Notification: 21 October 2010 
Vulnerability Type: XSS (Cross Site Scripting)
Status: Fixed by Vendor
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 when comments to articles allowed.
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.
Just add comment to any article:

Nice site. !http://123"onerror="javascript:document.location.href='http://htbridge.ch';"! 
Solution: Upgrade to the most recent version