No affiliation with Mozilla, just a very long time FF user.
They don't release this info so I don't know. That said, the best info I can find is here [0]. It claims that 87% of Firefox's contributions are from "mozilla". Red Hat also contribute. If you dig into some of Mozilla's outgoings, a lot of their non-employee outgoing spend is going on paying other vendors to work on their software. At least some of these looks like "paying people to work on firefox but not mozilla employees" - maybe it's EOR/contracting stuff. There is a huge outlier in André Bargull too, but it looks like as far as this analysis is concerned mozilla are absolutely integral to the current state of FF.
