W-Agora 4.20 XSS

2006.05.09
Risk: Low
Local: No
Remote: Yes
CWE: CWE-79


CVSS Base Score: 4.3/10
Impact Subscore: 2.9/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: None
Integrity impact: Partial
Availability impact: None

PLEASE NOTE: I am not sure if HTML is an option. I looked through the Administration panel and did not see an option for it, and the fact that there is no BBcode leads me to believe that this is the method of BBCode/etc. W-Agora is a fairly 'nice' bulletin board written in PHP. It allows multiple 'boards' (i.e. one with my forums and then one with yours) and has a nice administration panel. EXPLANATION: Also, W-Agora allows users to post HTML - not everything you'd think, as things like script, frame, body, html, etc are stripped. It also strips out 'on' anything, so you'd think that you cannot execute code -- right? No. The regex to clean out 'on'anything is like this: [code]' on([a-zA-Z]*)?=(.*)?'[/code] If you don't see the problem, let me explain: The filter expects that the = will come RIGHT after the On*! Therefore, if we put a space between it and the =, we do not match up against it and it will let it pass! Example: [code]<b onMouseOver =eval('alert(/xss/)')>hi</b>[/code] This renders both in IE & Firefox. =D USAGE: Since W-Agora can be configured to either set all userinfo in cookies or completely rely on sessions, this is mixed. If you find a site that uses cookies, you could use this to steal them. Shouts: digi7al64 - PrOtOn - Lockdown - WhiteAcid Video @ http://dynxss.whiteacid.org/videos/w-agora420xss.rar :: 899kb


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