Comment 4 for bug 752376

(For anyone hitting this, a simple workaround is just to double-click the file in a file manager like nautilus.)

FWIW, I filed https://bugzilla.mozilla.org/show_bug.cgi?id=652863 for this on the Mozilla side -- I'm not sure what will result of that though - it may end up being resolved as not-a-bug-in-Firefox.