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PR07-38 - XSS on sIFR

Vulnerability found:
12 November 2007
Vendor informed:
19 November 2007
Severity level:
Medium
Credits:
Jan Fry of ProCheckUp Ltd (www.procheckup.com)
Description:
Sites using sIFR to render fonts/text are vulnerable to a vanilla XSS within the "txt" parameter processed by the actionscript in the '<fontname>.swf' flash file.

Consequences

An attacker may be able to cause execution of malicious scripting code in the browser of a user who clicks on a link to the target website, or visits a malicious website that requests such link.

This type of attack can result in non-persistent defacement of the target site, or the redirection of confidential information (i.e.: session IDs) to unauthorised third parties.

BID

27394

Note

the victim user does NOT need to be authenticated for this vulnerability to be exploitable.

CVE reference

CVE-2008-0438

Successfully tested on

sIFR 2.0.2
Proof of concept:
{att:bold}- HTML injection PoC {att:/bold}

Provided the victim is tricked to load the following URL, he/she would be redirected to a third-party site.

https://target.tld/<fontname>.swf?txt=<a href="http://www.procheckup.com">click me!</a>

{att:bold}- XXS PoC {att:/bold}

http://target.tld/fonts/FuturaLt.swf?txt=%3Ca%20href=%22javascript:alert(document.cookie)%22%3Eclick%20me!%3C/a%3E&textalign=left&offsetTop=-2&textcolor=
How to fix:
This vulnerability has been fixed on Novemberborn sIFR 2.0.3 and Novemberborn sIFR 3r278.
References:
http://www.procheckup.com/research/views/vulnerabilities

http://www.mikeindustries.com/sifr

http://novemberborn.net/sifr

Legal:
Copyright 2008 Procheckup Ltd. All rights reserved.

Permission is granted for copying and circulating this Bulletin to the Internet community for the purpose of alerting them to problems, if and only if, the Bulletin is not edited or changed in any way, is attributed to Procheckup, and provided such reproduction and/or distribution is performed for non-commercial purposes. Any other use of this information is prohibited. Procheckup is not liable for any misuse of this information by any third party.
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