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Internet Explorer “Print Table of Links” Cross-Zone Scripting Vulnerability
Author: Aviv Raff
http://aviv.raffon.net/
Summary
Internet Explorer is prone to a Cross-Zone Scripting vulnerability in
its “Print Table of Links” feature. This feature allows users to add to
a printed web page an appendix which contains a table of all the links
in that webpage.
An attacker can easily add a specially crafted link to a webpage (e.g.
at his own website, comments in blogs, social networks, Wikipedia,
etc.), so whenever a user will print this webpage with this feature
enabled, the attacker will be able to run arbitrary code on the user’s
machine (i.e. in order to take control over the machine).
Affected version
Internet Explorer 7.0 and 8.0b on a fully patched Windows XP.
Windows Vista with UAC enabled is partially affected (Information Leakage only).
Earlier versions of Internet Explorer may also be affected.
Technical details
Whenever a user prints a page, Internet Explorer uses a local resource
script which generates an new HTML to be printed. This HTML consists of
the following elements: Header, webpage body, Footer, and if enabled,
also the table of links in the webpage.
While the script takes only the text within the link’s inner data, it
does not validate the URL of links, and add it to the HTML as it is.
This allows to inject a script that will be executed when the new HTML
will be generated.
As I said in a previous post, most of the local resources in Internet
Explorer are now running in Internet Zone. Unfortunately, the printing
local resource script is running in Local Machine Zone, which means that
any injected script can execute arbitrary code on the user’s machine.
Proof of Concept
The following is an example of a URL which executes Windows Calculator:
http://www.google.com/?q=<script defer>new ActiveXObject(“Wscript.Shell”).run(“calc”)</script>
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<html>
<body>
Print me with table of links to execute calc.exe
<a href=”http://www.bla.com?x=b<script defer >var x=new ActiveXObject(’WScript.Shell’);x.Run(’calc.exe’);</script>a.c<u>o</u>m”></a>
<script>window.print();</script>
</body>
</html>
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