Some buttons such as the new tab button are distorted. This was the series of changes after which I noticed this (Initially I was using firefox 41 on fedora 21-64 bit system with XFCE desktop): - Upgraded fedora to 22 - Installed LXDE desktop (along with XFCE) - Installed atolm theme (http://gnome-look.org/content/show.php/Atolm?content=136789). Just extracted the archive content to ~/.themes - switched to this theme - used the rodent (XFCE) icon theme Till this point I had not opened firefox and so I do not know at what stage this problem occurred. I decided to remove LXDE and switch back to XFCE. I thought that this distortion of icons possibly happened because of some incompatible Openbox desktop configuration. This problem persisted in XFCE desktop too. I tried changing themes to see if some bug with the theme is causing these things but it remained so. I reinstalled firefox but still the problem persists. There is no option in the customize menu to fix this. Moreover, firefox menus are not using the gtk-theme. I updated my firefox in another fedora-21 system and installed the same gtk-theme and this one is fine. The menus are according to the gtk-theme and the icons are not distorted.