Actually, it is still true. Electroloysis split up Firefox into multiple processes, but not every site gets its own process. Work is underway to change this an

Actually, it is still true. Electroloysis split up Firefox into multiple processes, but not every site gets its own process. Work is underway to change this and achieve full site isolation in https://wiki.mozilla.org/Project_Fission https://wiki.mozilla.org/Project_Fission. (Disclosure: I work for Mozilla, but not on this)