I've updated my plasma today. Looks like firefox icon is deleted somehow. I've checked git repo. There is no such file named "firefox.svg" in https://quickgit.kde.org/?p=breeze.git&a=tree&h=dff08cd23121584e61e16e8b5e9b4c3796696100&hb=454483b51f86f0b15403ffdf6643735100080565&f=icons%2Fapps%2F48 Reproducible: Always
It's not missing, I removed because it's a trademarked logo brand and it shouldn't be in the main theme. The icon and other trademarked logos are on the Github repo https://github.com/NitruxSA/breeze-icon-theme (trademarked-logos) branch.
Did you decide that for yourself or did actual legal problems occur? KDE shipped custom icons even for proprietary applications since its forever.
I was told to remove it from the main theme.
(Ah snap) not by Mozilla, by Thomas (colomar).