bugtraq - WebCT Campus Edition 4.1 - Cross site scripting using CSS @import

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Message-ID: <20040329000119.GA387@zappa.simcool.com>
Date: Sun, 28 Mar 2004 19:01:19 -0500
From: Simon Boulet <simon.boulet@...ahost.net>
To: bugtraq@...urityfocus.com
Subject: WebCT Campus Edition 4.1 - Cross site scripting using CSS @import



Name: WebCT Campus Edition 4.1 - Cross site scripting using CSS @import
Release date: 2004/03/29
Application: WebCT Campus Edition 4.1 (4.1.1.5), possibly others
Vendor URL: http://www.webct.com/ (WebCT Inc.)
Author: Simon Boulet <simon.boulet@...ahost.net>

Legal Notice:
--------------------
This Advisory is Copyright (c) 2004 Simon Boulet
You may distribute it unmodified.
You may NOT modify it and distribute it or distribute parts of it  
without the author's written permission.

Disclaimer:
--------------------
The information in this advisory is believed to be true though it may  
be false. The opinions expressed in this advisory are my own and not of  
any company. The usual standard disclaimer applies, especially the fact  
that Simon Boulet is not liable for any damages caused by direct or  
indirect use of the information or functionality provided by this  
advisory. Simon Boulet bears no responsibility for content or misuse of  
this advisory or any derivatives thereof.

Description:
--------------------
WebCT Campus Edition is a course management system which allows the  
delivery of course material and assessments online. It is used by many  
colleges and universities world-wide.

This version of WebCT allows HTML tags to be inserted when posting new  
messages on a forum. Although WebCT filters dangerous tags insertion,  
it is possible to bypass this security, resulting in a cross-site  
scripting (XSS) vulnerability.

Problem:
--------------------
Microsoft Internet Explorer allows execution of JavaScript code inside  
the CSS @import url() parameter. A user could post a specially crafted  
message using the @import method to insert malicious JavaScript code in  
a forum thread. The inserted code could potentially steal session  
cookies from users accessing the given thread.

In most circumstances, this problem would result in the user’s session  
hijacking (ex.: stealing the session id). But unfortunately, WebCT  
Campus Edition stores sensitive information, such as login name and  
password, directly in user’s cookies.

Furthermore, the file upload module, which allows students to upload  
files directly through WebCT, seems to be vulnerable to the same issue.
	
Example:
--------------------
A user could post the following code through a forum thread:

<style type="text/css">
@import url(javascript:alert(document.cookie));
</style>

Solution:
--------------------
The vendor was contacted on 2004/03/18 and has quickly addressed this  
issue. Updates (untested) are available for the following products:

WebCT CE 4.1 SP2 Hotfix 40832
http://download.webct.com/ce+/4.1/hotfixes/41sp2_hotfix_rel_notes.html

WebCT CE 4.0 SP3 Hotfix 40833
http://download.webct.com/ce+/4.0/hotfixes/40sp3_hotfix_rel_notes.html

WebCT CE 3.8.4 Hotfix 8
http://download.webct.com/ce+/3.8/hotfixes/384_hotfix_rel_notes.html