Hi all I'm seeing the same behaviour here on GNOME 3.14.0 . It's on Fedora 21, showing that this is an upstream bug not a Debian specific bug.
I'm also observing it with Kerbal Space Program in full screen, so it's not only Iceweasel / Firefox. Interestingly, modified clicks (alt-click, shift-click, etc) are passed to the app fine, as are mouse-moved events. It's only unmodified left and right click or drag events that seem to pass through and trigger an interaction with the window "behind", which might be the desktop or another app. One result is that focus is often lost unexpectedly, so another window pops into focus "on top" of the full screen app. -- Craig Ringer Technical writing: http://blog.ringerc.id.au and http://blog.2ndquadrant.com
