Inrtra Forum Cross Site Scripting Vulnerabillity

Software: Inrtra Forum (Perl CGI)
Vendor: http://www.diburim.co.il/
Versions: Single version was created
Bug: Cross Site Scripting Vulnerabillity
Risk: Low
Exploitation: Remote with browser
Date: 24 Jan 2004
Author: Rafel Ivgi, The-Insider
E-Mail: the_insider mail com
Web: http://theinsider.deep-ice.com/

1) Introduction
============
Inrtra Forum is israel's most common free/paid forum service provider.
Forum as important as this cannot have risks such as Cross Site Scripting.
Any attacker can fake messages, and betray the trust of all the people who
belive that links involved with this forum are safe.

2) Bug
======
The Vulnerabillity is Cross Site Scripting.
The vulnerable form fields are "use_last_read" and "forum".
If an attacker will request the following url from the server:

+http://<host>/cgi-bin/forumsdb/intraforum_db.cgi?forum=<script>alert('sda')</script>&read=&alias=&redir_flag=true
Or
+http://<host>/cgi-bin/forumsdb/intraforum_db.cgi?forum=7940&alias=dbr&read=000965-000964&session=FFFF&use_last_read="><script>alert('XSS')</script>

XSS appears and the server allows an attacker to inject & execute scripts.

In the words of securityfocus.com :
~~~~~~~~~~~~~~~~~~~~~~~~~~
If all of these circumstances are met, an attacker may be able to exploit this issue via a malicious link containing arbitrary HTML and script code as part of the hostname.
When the malicious link is clicked by an unsuspecting user, the attacker-supplied HTML and script code will be executed by their web client. This will occur because the server will echo back the malicious hostname supplied in the client's request, without sufficiently escaping HTML and script code.

Attacks of this nature may make it possible for attackers to manipulate web
content or to steal cookie-based authentication credentials. It may be possible to take arbitrary actions as the victim user.

3) The Code
===========
Example:
+http://www4.diburim.co.il/cgi-bin/forumsdb/intraforum_db.cgi?forum=<script>alert('XSS')</script>&read=&alias=&redir_flag=true

CODE
http://<host>/cgi-bin/forumsdb/intraforum_db.cgi?forum=7940&alias=dbr&read=000965-000964&session=FFFF&use_last_read="><script>alert('XSS')</script>
http://<host>/cgi-bin/forumsdb/intraforum_db.cgi?forum=<script>alert('XSS')</script>&read=&alias=&redir_flag=true