PR07-38: XSS on sIFR Jan 22 2008 10:31AM
ProCheckUp Research (research procheckup com)
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&t
extcolor=

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.

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