Monday, November 22, 2010

XSS track got ninja stealth skills thanks to HTML5

XSS-Track, a point of concept project on how to track users through XSS vulnerability today got even better: now it can change URL in browser address bar as you navigate through the site, making it even more transparent for the victim.

It is possible thanks to a HTML5 feature - window.history.pushState(). It was created for AJAX websites so that they could easily change window location bar and manipulate history. Read more about the it on WHATWG site.

It's a great and convenient feature for developers - for example, AJAX apps can now easily support back & forward buttons without resorting to URI fragment identifier (#) hacks. But it can also be used for malicious purposes. Basically, in HTML5 you can no longer trust the location bar. For security reasons, specs say you can only change a path (i.e. not hostname, port etc.) and of course it is subject to same-origin restrictions but that is enough for XSS-Track. So now we have these convenient functions in XSS-track source code:

var getPath = function(url) {
  return url.match(/(\/.*)/)[1];

var changeAddressBar = function(url) {
  try {
    // html5 goodness - should work in Safari, Chrome, FF 4
    window.history.pushState({}, "", getPath(url));
  } catch(e) {}

and navigating a link within vulnerable domain will update the address bar path accordingly, making XSS-track practically invisible (unless you click an external link).

window.history.pushState() works in Chrome 5, Safari 5 and Firefox 4 and more browsers will come in future. When it's not available, XSS-Track will just leave the URL of a vulnerable page, so we're forward compatible. Try and hack the demo site to see the effects in one of those browsers to see it in action. HTML5 FTW!

Saturday, November 6, 2010

XSS-Track: How to quietly track a whole website through single XSS

XSS is #1 threat in web application security. We all know it's pretty common, from time to time we encounter a website where a single input field is vulnerable. Happily we send out alert(document.cookie) only to find out that session cookie is httpOnly (it's a good sign!). On the other side we know that XSS gives us, white hats, an almost unlimited potential on how to alter the vulnerable page. We can:
  • deface it,
  • steal user's form values
  • redirect to form a phishing attack
  • look at cookies
  • try to send malware through a drive-by download attack
  • and many more...
However, what to do if we found a vulnerability on one page, and all the interesting things are on the other page on the same domain? Say, the vulnerability is on and we'd really like to steal user's credentials from Of course, with JS it's possible, but usually it's a difficult manual process to construct such payload. Today I'll present a way that makes it dead easy to:
  • track user's actions on a vulnerable website (clicks, form submits),
  • track outside links,
  • monitor pages content and report any interesting HTML elements (e.g. the secret credentials)
All of this is possible with a single injected script - think XSS-injected Google Analytics! With just one XSS vulnerability on any page an attacker gets information about all browsing actions of unsuspecting user. Demo inside!