From their careers site:

"Mozilla is a global organization, and this role is available in our offices in the European Union, U.S., Canada, or home-based in the U.S., Canada, and European countries where Mozilla has a legal entity. You must have work authorization in one of these countries."

This is not remote work.

I'm not sure how "home-based" is not "remote". Yes, there are restrictions on possible countries where the employee lives, to do with legal bits like payroll taxes and whatnot.