Björn Engelmann, Joachim Posegga, and LocalRodeo developer Martin Johns have authored an excellent paper on a new Cross-site Scripting detection system called XSSDS.  Stay tuned to noxss.org for a new browser extension based on this technology.  The XSSDS approach is similar in some ways to the IE8 XSS Filter approach, although it’s worth noting that until recently Martin’s team had…


XSS-Focused Attack Surface Reduction

All web browsers expose what have been referred to as XSS “attack vectors” – various techniques that XSS attacks can leverage to achieve script execution.  The best and most well regarded list of these behaviors is RSnake’s XSS Cheat Sheet. The existence of these attack vectors can at minimum present a challenge to filters and…


Video Roundup (Martin Johns and more!)

Recently I got Martin Johns connected with Helen Wang’s group in Microsoft Research.  Check out Martin’s excellent talk @MSR, Secure Code Generation for Web Applications. Here are a few other gems I discovered on content.digitalwell.washington.edu: Techniques and Tools for Engineering Secure Web ApplicationsGary Wassermann, 3/13/2008 Improving Software Security with Precise Static and Runtime AnalysisBenjamin Livshits, 6/26/2006…


IE8 XSS Filter design philosophy in-depth

It’s great to see some positive reaction to the potential of our XSS Filter.  Now we just need to deliver! In this blog post I’ll try to shed some light on our design philosophy. To understand how we have arrived at our current filtering approach, it is useful to look back to the XSS Filter’s…


Code length dependent obfuscation

Wow, it’s been a long time!  Hopefully I can find more time to blog over the next couple of months.In any event, my paper from last year really could use some updates.  Among other things there are a whole new slew of “Usual Suspect” vulnerabilities to document.  For this post I’ll focus on documenting an…



Giorgio Maone’s new ABE project looks pretty cool. Exposing the loose and often unnecessary boundaries between web applications shines a different light on some old problems in web application security.  Enforcing greater formalization and limiting the attack surface presented by these boundaries is a great thing. Yeah, yeah, I know, Giorgio doesn’t like us, etc…, whatever.  😉


IE 8 XSS Filter Architecture / Implementation revealed + some other news

I’ve just posted some detail on the Internet Explorer 8 XSS Filter Architecture / Implementation over on the SWI Blog.  It would be great to get some feedback and answer any questions you may have — just drop me a mail using the Email link to the left. In other news, Gareth Heyes has been spending some time testing the XSS Filter implementation.  Gareth has written…


Good Bug

Credit goes to Alex “Kuza55” Kouzemtchenko for identifying a weakness in the XSS Filter OBJECT tag heuristic.  The original heuristic failed to properly sanitize OBJECT tags with the DATA attribute set.  Alex found that it is possible to use the DATA attribute to instantiate the PDF handler, then reference content to be loaded using a PARAM element. …


IE8 goes on the offensive against XSS!

IE has announced the new XSS Filter feature which will debut in IE8 Beta 2!  Stay tuned to my blog in the coming weeks for more details on how the filter works, its history, its limitations, and some lessons learned during the development process.


New webappsec tools

Chris Weber’s Watcher: http://www.lookout.net/2009/03/20/watcher-security-tool-a-free-web-app-security-testing-and-compliance-auditing-tool/ Watcher plugs into the Fidder HTTP proxy and monitors for all sorts of web app vulns, from the common to the obscure. Gareth Heyes’ XSS Rays: http://www.thespanner.co.uk/2009/03/25/xss-rays/ XSS Rays runs in the browser as a bookmarklet and scans for XSS on demand.