DOM-based XSS was first revealed to the world back in 2005 by Amit Klien, when it was an interesting theoretical vulnerability. In 2012, with the push towards Web 2.0 well into the mainstream, DOM-based XSS has become a very commonly uncovered and exploited vulnerability, but it’s poorly understood.
This talk will focus on the full range of issues around DOM-based XSS. It will start with a discussion of the technical details of the vulnerability, the true nature of the risk it introduces (both likelihood and impact), and some new terminology and updated definitions about what truly is a DOM-based XSS vulnerability as compared to the standard Stored and Reflected XSS that the community is well aware of. It will then discuss the difficulties that security analysts face when trying to find DOM-based XSS flaws, and provide recommended analysis techniques that help move DOM-based XSS discovery from an art towards more of a science. And finally, it will discuss simple techniques for avoiding DOM-based XSS issues in the first place as well as how to mitigate issues that are uncovered during a security review.
