A dangerous combination of browser features

As browsers gain more and more features, the possibility increases for interesting or dangerous interactions between these features. I was recently playing with a couple of new browser features -- <canvas> and SVGs -- and found a cross-domain leak in the development version of Webkit:

http://scary.beasts.org/security/CESA-2008-007.html

Fortunately, no production versions of the major browsers are affected - and forearmed with this information, they can keep it that way. The only production browser I found that supports all of the required pieces is Opera 9.52, and they deserve some serious credit for getting the security check correct.