https://bugs.winehq.org/show_bug.cgi?id=41175
--- Comment #6 from Ruslan Kabatsayev b7.10110111@gmail.com --- (In reply to winetest from comment #5)
It's just that the original bug report was against firefox 47 and 48. Now we don't know if the fix is in wine or firefox.
I've just checked wine-1.9.17 with current Firefox 51.0.1, and the original bug did reproduce. So it's really fixed in Wine, not in Firefox.