Re: [Full-Disclosure] Cross-Site Scripting in Unparsable XML Files (GM#013-IE)

From: jelmer (kuper237at_private)
Date: Tue Jun 17 2003 - 06:57:28 PDT

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    hi greymagic,
    
    First off i can't reproduce this on my fully patched ie6
    
    Second you should be able to have ie render any html page as a xml file like
    this
    
    <object type="application/xml" data="http://www.yahoo.com" width="500"
    height="500">
    </object>
    
    Generaly html files are not well formed xml so it shouldnt be difficult to
    get this to work on just about any site
    
    --jelmer
    
    
    ----- Original Message ----- 
    From: "GreyMagic Software" <securityat_private>
    To: <full-disclosureat_private>
    Sent: Tuesday, June 17, 2003 12:09 PM
    Subject: [Full-Disclosure] Cross-Site Scripting in Unparsable XML Files
    (GM#013-IE)
    
    
    > GreyMagic Security Advisory GM#013-IE
    > =====================================
    >
    > By GreyMagic Software, Israel.
    > 17 Jun 2003.
    >
    > Available in HTML format at http://security.greymagic.com/adv/gm013-ie/.
    >
    > Topic: Cross-Site Scripting in Unparsable XML Files.
    >
    > Discovery date: 18 Feb 2003.
    >
    > Affected applications:
    > ======================
    >
    > Microsoft Internet Explorer 5.5 and 6.0.
    >
    > Note that any other application that uses Internet Explorer's engine
    > (WebBrowser control) is affected as well (AOL Browser, MSN Explorer,
    etc.).
    >
    >
    > Introduction:
    > =============
    >
    > Internet Explorer automatically attempts to parse any XML file requested
    > individually by the browser. When the parsing process is successful, a
    > dynamic tree of the various XML elements is presented. However, when a
    > parsing error occurs Internet Explorer displays the parse error along with
    > the URL of the requested XML file.
    >
    >
    > Discussion:
    > ===========
    >
    > We have found that in some cases the displayed URL is not filtered
    > appropriately, and may cause HTML that was passed in the querystring of
    the
    > URL to be rendered by the browser. This creates a classic cross-site
    > scripting attack in almost any XML file that MSXML fails to read.
    > Practically, this means that leaving XML files on your server that can't
    be
    > parsed correctly by Internet Explorer and MSXML is exposing the site to a
    > global Cross-Site Scripting attack.
    >
    > We have been able to reproduce this problem in various setups, but we
    > couldn't pinpoint the vulnerable component reliably enough. It is most
    > likely an MSXML issue, and not a flaw in Internet Explorer itself.
    >
    >
    > Exploit:
    > ========
    >
    > This sample shows the basic URL for injecting content:
    >
    >
    http://host.with.unparsable.xml.file/flaw.xml?>alert(document.cookie)
    > </script>
    >
    >
    > Demonstration:
    > ==============
    >
    > We put together a simple proof of concept demonstration, which can be
    found
    > at http://security.greymagic.com/adv/gm013-ie/.
    >
    >
    > Solution:
    > =========
    >
    > Microsoft was notified on 20-Feb-2003. They reported that they were able
    to
    > reproduce this flaw on IE6 Gold, and no other version. Our research showed
    > different, yet inconsistent results (see "Tested on" section for details).
    >
    >
    > Tested on:
    > ==========
    >
    > IE5.5 NT4.
    > IE6 Win98.
    > IE6 Win2000.
    >
    >
    > Disclaimer:
    > ===========
    >
    > The information in this advisory and any of its demonstrations is provided
    > "as is" without warranty of any kind.
    >
    > GreyMagic Software is not liable for any direct or indirect damages caused
    > as a result of using the information or demonstrations provided in any
    part
    > of this advisory.
    >
    >
    > Feedback:
    > =========
    >
    > Please mail any questions or comments to securityat_private
    >
    > - Copyright © 2003 GreyMagic Software.
    >
    > _______________________________________________
    > Full-Disclosure - We believe in it.
    > Charter: http://lists.netsys.com/full-disclosure-charter.html
    



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