Vulnerability ID: HTB23036
Reference: http://www.htbridge.ch/advisory/xss_in_fast_secure_contact_form.html
Product: Fast Secure Contact Form wordpress plugin
Vendor: Mike Challis  ( http://www.fastsecurecontactform.com ) 
Vulnerable Version: 3.0.3.1 and probably prior
Tested on: 3.0.3.1
Vendor Notification: 27 July 2011 
Vulnerability Type: XSS (Cross Site Scripting)
Status: Fixed by Vendor
Risk level: Medium 
Credit: High-Tech Bridge SA Security Research Lab ( http://www.htbridge.ch/advisory/ ) 

Vulnerability Details:
High-Tech Bridge SA Security Research Lab has discovered vulnerability in Fast Secure Contact Form wordpress plugin, which can be exploited to perform cross-site scripting attacks.

Input appended to the URL after /wp-content/plugins/si-contact-form/captcha/test/index.php is not properly sanitised before being returned to the user.
This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of affected website.

The following PoC code is available:

http://[host]/wp-content/plugins/si-contact-form/captcha/test/index.php/%22%3E%3Cscript%3Ealert%28document.cookie%29;%3C/script%3E
Solution: Upgrade to the most recent version