Don't tease us - what was your exploit? Just from the description, I'm happy taking a guess that this is going to involve somehow exploiting the browser cache (

Don't tease us - what was your exploit? Just from the description, I'm happy taking a guess that this is going to involve somehow exploiting the browser cache (e.g. via timing how long it takes to request an image from another domain that may or may not have previously been cached) to determine whether the user has visited a page. That was first written up by academics decades ago, and has since been independently invented by several people (me included), but wasn't fixed as of whenever I last checked a couple of years ago. Is my wild guess right? :)