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XSS hiding CSRF (was: Re: [oss-security] Mibew messenger multiple XSS)
From: "Steven M. Christey" <coley () rcf-smtp mitre org>
Date: Wed, 1 Feb 2012 17:23:34 -0500 (EST)


Funny, the CVE team was discussing this curiosity just today.

In the Mibew case, the PoC code has POST forms that invoke scripts like "/operator/ban.php" and "/operator/settings.php". These are almost certainly administrative functions that probably shouldn't be reachable at all. Thus, these might be better identified as CSRF issues at their core, instead of XSS.

It seems that some researchers report XSS in administrator modules, but they omit when you need to use CSRF in order to get the administrator to perform the XSS. So, the primary issue is often CSRF, and XSS is only resultant (since, in many cases, the admin already has privileges to edit HTML). The vuln DBs are starting to catch up with this "trend" in vuln reporting, so there is a very slow shift towards identifying CSRF as the core problem. However, CSRF is in the eye of the beholder, in that you often need to know the INTENDED functionality of the application before you can interpret whether things are CSRF versus regular functionality, versus good old XSS.

Note that this kind of XSS-hiding-CSRF issue is not necessarily tied to admin functionality, but that's where it's a strong indicator that a researcher might be ignoring CSRF.

Sometimes, though, it can be difficult to determine whether XSS or CSRF is at the root, even if you're dealing with admin functionality. For example, maybe an admin program will check for CSRF and fail, but include the original form in its error response, possibly enabling XSS. Or, maybe there are TWO issues at play - maybe a victim can be CSRF'ed to make posts on their behalf, and also a secondary issue where the victim can become an attacker and XSS other people (with or without CSRF).

Unfortunately, I strongly suspect that the number of XSS-hiding-CSRF reports will grow :-(

For people who investigate vuln reports closely, please keep this trend in mind. If you are a researcher, consider whether XSS or other issues are really legitimate functionality that is only reachable by targeting the victim with CSRF; if that's the case, then the CSRF is "primary" and the XSS is "resultant" and not a separate vulnerability - and if your targeted application has CSRF, then maybe there's a more powerful impact than just XSS. (For example, depending on how settings / configuration is implemented, you might be able to get code execution out of it.)

- Steve


On Wed, 1 Feb 2012, Kurt Seifried wrote:

On 01/31/2012 08:22 AM, Henri Salo wrote:
This seems to need 2012 CVE-identifier.

Advisory: http://seclists.org/bugtraq/2012/Jan/177
Codseq own advisory: http://www.codseq.it/advisories/mibew_messenger_multiple_xss
OSVDB: http://osvdb.org/show/osvdb/78663
Secunia: http://secunia.com/advisories/47787/

At the moment http://mibew.org/ does not work for me.

- Henri Salo

Please use CVE-2012-0829 for this issue.

P.S. for some reason OSVDB lists this as a CSRF issue (?) which is
mentioned in the advisory but not really shown.

--
Kurt Seifried Red Hat Security Response Team (SRT)



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