Muslims even admit that at least one of Mohammed's communications from "Allah" came from Satan.
Mohammed at one point states there are four Gods, Allah, and three female idols from the Kaaba. He takes this back later, says Satan tricked him ("oops, I plumb forgot about the whole 'monotheism' thing and couldn't tell one of God's communications apart from one of Satan's"), and the verses were struck from the Quran. That is the "Satanic Verses" controversy (the book by the same name deals with this, it was embarrassing enough that Muslims around the world decided they had to kill Rushdie).