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

From: Kevin Spett (kspettat_private)
Date: Tue Jun 17 2003 - 08:19:20 PDT

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    > <object type="application/xml" data="http://www.yahoo.com" width="500"
    > height="500">
    > </object>
    
    This produces a warning in IE6 before it does anything with it.
    
    
    Kevin Spett
    SPI Labs
    http://www.spidynamics.com
    
    
    > 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
    >
    > _______________________________________________
    > Full-Disclosure - We believe in it.
    > Charter: http://lists.netsys.com/full-disclosure-charter.html
    >
    



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