vBulletin - XSS Filter Bypass within Profile Customization


Versions Affected: 4.0.8 PL1 (3.8.* is not vulnerable.)

Info:
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External Links:
http://www.vbulletin.com

Credits: MaXe (@InterN0T)


-:: The Advisory ::-
vBulletin is prone to a Persistent Cross Site Scripting vulnerability within the
Profile Customization feature. If this feature is not enabled the vulnerability
does not exist and the installation of vBulletin is thereby secure.

Within the profile customization fields, it is possible to enter colour codes,
rgb codes and even images. The image url() function does not sanitize user
input in a sufficient way causing vBulletin to be vulnerable to XSS attacks.

With the previous patch for vBulletin 4.0.8 PL1, most attacks were disabled
however it is possible to bypass this filter and inject data which is then executed
effectively against though not limited to Internet Explorer 6.

Proof of Concept:
url(vbscript:msgbox("X/SS"))


-:: Solution ::-
Update vBulletin to version: 4.0.8 PL2


Disclosure Information:
- Vulnerability found and researched: 18th November 2010
- Disclosed to vendor (Internet Brands): 18th November
- Patch from Vendor available: 19th November
- Disclosed at: InterN0T, Full Disclosure, Bugtraq and Exploit: 20th November


References:
http://forum.intern0t.net/intern0t-advisories/3398-vbulletin-4-0-8-pl1-cross-site-scripting-filter-bypass-within-profile-customization.html
http://forum.intern0t.net/intern0t-advisories/3349-vbulletin-4-0-8-persistent-cross-site-scripting-via-profile-customization.html