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vBulletin XSS Security Bug
From: Sp.IC <SpeedICNet () Hotmail Com>
Date: 18 Oct 2002 12:08:55 -0000

.:: vBulletin XSS Security Bug

vBulletin is a powerful and widely used bulletin board system, based on 
PHP language and MySQL database. One of its features is the usage of 
templates to modify the boards look. I discovered lately a Cross-Site 
Scripting vulnerability that would attackers to inject maleficent codes 
and execute it on the clients browser.

+ Vulnerable Versions:

    - Jelsoft vBulletin 2.2.8.
    - Jelsoft vBulletin 2.2.7.
    - Jelsoft vBulletin 2.2.6.
    - Jelsoft vBulletin 2.2.5.
    - Jelsoft vBulletin 2.2.4.
    - Jelsoft vBulletin 2.2.3.
    - Jelsoft vBulletin 2.2.2.
    - Jelsoft vBulletin 2.2.1.
    - Jelsoft vBulletin 2.2.0.
    - Jelsoft vBulletin 2.0.2.
    - Jelsoft vBulletin 2.0.1.
    - Jelsoft vBulletin 2.0.0.
    - Jelsoft vBulletin 2.0.0 Candidate 3.
    - Jelsoft vBulletin 2.0.0 Candidate 2.
    - Jelsoft vBulletin 2.0.0 Candidate 1.
    - Jelsoft vBulletin 2.0.0 Beta 5.
    - Jelsoft vBulletin 2.0.0 Beta 4.
    - Jelsoft vBulletin 2.0.0 Beta 4.1.
    - Jelsoft vBulletin 2.0.0 Beta 3.
    - Jelsoft vBulletin 2.0.0 Beta 2.
    - Jelsoft vBulletin 2.0.0 Beta 1.
    - Jelsoft vBulletin 2.0.0 Alpha.

+ Details:

In global.php there is a variable [$scriptpath], the value of it is the 
referred URL that the client came from. Move on to admin/functions.php, 
in show_nopermission function the $scriptpath is called as a global 
variable. The content of the variable gets printed in the 
error_nopermission_loggedin template without filtering it. So if we pass 
some tags and script codes in the URL and refresh the page it will be 
printed in the no permission template. The same thing with $url variable 
which print its contents in many templates.

+ Exploit:

Note: Tested on Microsoft Internet Explorer 6.0 and vBulletin.com:

    - Go to usercp.php?s=[Session ID]">&lt;Script&gt;alert
(document.cookie);&lt;/Script&gt; [You can use it wherever 
error_nopermission_loggedin get printed].
    - A pop-up window will appear and you'll receive an error message.
    - Then log in.
    - Go back to the previous pages where you left the login form.
    - Then the pop-up window will appear again containing the User ID and 
Password Hash.

The same thing with $url templates.

+ Solution:

    - Forum administrator can add some codes that will check the referred 
URL and filter its inputs or upgrade to vBulletin 3.0.

+ Links:

    - Http://www.vBulletin.com

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