On Björn Ironside's wikipedia page, there is a bit where it says that Björn and his navy fought the Arabs near Gibraltar. He lost the battle and 40 ships, due to the Arabs using "Greek Fire". I always read that the Byzantines kept the recipe for Greek Fire a really well-guarded secret, which was lost with the end of the empire. Is it possible the Arabs managed to get a copy of the recipe, or did they make their own version? Or was there some kind of "black-market" for unique weapons, where a greedy Byzantinian could've sold some of the original stuff? Also, if the Arabs had the their own version of "Arab Fire", is the recipe for their version known?
Greek fire is often used as a general term for any incendiary weapon. The greek fire used by the arabs was most likely not the greek fire of the byzantines.