Universal Windows apps (like settings) do not use the OS titlebars (they just look similar) and are not skinnable.
Firefox for reasons best known to the devs, chose to implement their own fake titlebars. Unfortunately this is outside our control. This is also only the case on Windows 10, I think on Windows 7/8 they use standard titlebars and are skinned.
What issues are you having with NOD32 and WindowBlinds?