Since three updates ago there are white bars on three sides of my Firefox window whenever I disable the title bar. (The bars should be visible if you open the first picture I've attached over a coloured background. The second picture shows the bars disappearing when the title bar is switched on.) This problem persists in Safe Mode and even after a fresh installation of Firefox, so I am confident that my add-ons and themes are not the issue. The bars also show up when using the Firefox default theme, so a custom theme is not the problem either. I have also tried, to no avail: Updating my graphics driver, changing my screen scaling, cleaning the registry. And of course simply restarting my computer. I am at a loss as to what the issue is or how I can fix it.