While researching my previous report on MSIE7 browser entrapment, I noticed that Firefox is susceptible to a pretty nasty, and apparently easily exploitable memory corruption vulnerability. When a location transition occurs and the structure of a document is modified from within onUnload event handler, freed memory structures are left in inconsistent state, possibly leading to a remote compromise. A quick test case that crashes while trying to follow partly user-dependent corrupted pointers near valid memory regions (can be forced to write, too): http://lcamtuf.coredump.cx/ietrap/testme.html This also crashes MSIE7 with a seemingly harmless NULL pointer bug (didn't research it - do your homework). Firefox problem is being tracked here: https://bugzilla.mozilla.org/show_bug.cgi?id=371321 /mz