ProCheckUp Security Advisory 2007.38

`PR07-38: XSS on sIFR  
  
Vulnerability Found: 12 November 2007  
  
Vendor contacted: 19 November 2007  
  
Vulnerability fixed: The issue remains unfixed. The developer of sIFR   
was contacted several times but did not respond.  
  
Severity: Medium  
  
Successfully tested on: sIFR 2.0.2  
  
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.  
  
Note: the victim user does NOT need to be authenticated for this   
vulnerability to be exploitable.  
  
  
HTML injection PoC:  
  
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>  
  
XSS PoC:  
  
http://target.tld/fonts/FuturaLt.swf?txt=%3Ca%20href=%22javascript:alert(document.cookie)%22%3Eclick%20me!%3C/a%3E&textalign=left&offsetTop=-2&textcolor=  
  
  
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.  
  
  
References:  
  
http://www.procheckup.com/Vulnerabilities.php  
  
http://www.mikeindustries.com/sifr  
  
  
Credits: Jan Fry of ProCheckUp Ltd (www.procheckup.com)  
  
  
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.  
`