User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/600.3.18 (KHTML, like Gecko) Version/7.1.3 Safari/537.85.12 Steps to reproduce: On latest nightly, html5 drag and drop no longer works. Example is http://www.html5rocks.com/en/tutorials/dnd/basics/ (scroll down to what is labeled final product just before the conclusion). Actual results: The drag event starts, and the square moves inwards. However, the square does not move with the mouse, and the drop event never occurs. Another example is google drive - if you start to drag a file into a folder, the file cannot be dragged. Apparently you can't attach multiple files to a bug. I've attached a video of the incorrect behavior - I'll try to add a video of the correct behavior soon. Expected results: This should work like it does in Firefox 35 - the draggable box moves with the mouse and the drop event occurs.

video of correct behavior in firefox 35

It should work in the nightly build if you disable the multiprocess feature (preferences/general/e10s)