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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

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.

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

The Kill-Bit FAQ - Part 1 of 3 posted to SVRD blog

Check out my ActiveX Kill-Bit FAQ which is now being posted to the SVRD blog . There are three parts, the first of which is now live. Parts two and three should be up by the end of the week.

An innovative new defense against cross-domain vulnerabilities

Cross-domain (or “Universal XSS”) vulnerabilities have long plagued modern script-enabled web browsers. Shuo Chen of Microsoft Research has developed a new type of defense against these vulnerabilities. A paper on this new approach has been accepted to

Notes on DNS Pinning

Christian Matthies has an excellent writeup on DNS Pinning (with diagrams!) If you're tuned into web app security you've probably noticed a lot of discussion around Anti DNS Pinning a.k.a. DNS Rebinding a.k.a. Quick-Swap DNS lately. You're likely to see

eval() and document.write(), meet Execute and ExecuteGlobal

Be on the lookout for these two VBScript statements that can be used to achieve the same effect as eval() and document.write(): Execute and ExecuteGlobal . Jonathan Ness pointed me to an exploit sample that was using Execute, presumably to trip up any

Recursive Obfuscation

Thanks to Jonathan Ness for pointing me to an example of a new obfuscation technique that attempts to thwart the eval() à alert() trick . Take a look at the following obfuscation script: 1 <script> 2 function N(F,D) 3 { 4 if (!D) D = ' "#%()-./012348:;<=>@ACEGHILMOPRTVWY\\]_abcdefghijlmnopqrstuvwxyz';

High-bit ASCII obfuscation

Here’s another new obfuscation technique I’ve seen in use on malicious web sites recently. Check out the following HTML: <html><meta http-equiv=content-type content='text/html; charset=us-ascii'></head><body>¼óãòéðô¾áìåòô¨¢Ôèéó

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

Analyzing Browser Based Vulnerability Exploitation Incidents

I've written up a paper that describes some useful tools/techniques for deconstructing web based exploits: Analyzing Browser Based Vulnerability Exploitation Incidents The paper started as a blog entry and it remains a blog entry at its core. But since
 
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