Since version 15 (I think), Firefox held a grip on the console window from which it was started. It would never exit as long as Firefox was running, and if the console window was forcibly closed, Firefox would vanish, too.
There is a hotfix in form of an extension available at
https://bugzilla.mozilla.org/show_bug.cgi?id=787313
which resolves this problem.
There is a hotfix in form of an extension available at
https://bugzilla.mozilla.org/show_bug.cgi?id=787313
which resolves this problem.