11th Jun 2002 [SBWID-5423]
COMMAND
Flash with embeeded Javascript bypass all browser & web sites
protections for CSS
SYSTEMS AFFECTED
All web sites allowing users to upload flash
PROBLEM
Obscure from EyeonSecurity [http://eyeonsecurity.net/] found a way to
use flash in cross site scripting.
Abstract
========
In this document we will be describing a loophole, with security
implications, found in many websites that allow Flash documents to be
inserted within HTML, or uploaded to the server. This paper relies on
the fact that a huge number of web surfers have installed Macromedia
Flash plugin/ActiveX control, for an attacker to launch a Cross-site
scripting attack. We will not go into a lot of detail in describing
Cross-site scripting attacks in general; However we hope that this
paper will explain how Flash documents can be used to inject JavaScript
into otherwise well filtered Web Applications.
See http://eyeonsecurity.net/papers/flash-xss.htm for more.
SOLUTION
Web sites should filter getURL() in uploaded flash objects.
see paper for more details.
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