Halo 5: Guardians sold 5 million copies in its first three months, this according to Frank O'Connor, the franchise development director at 343 Industries. The news comes via a post on a NeoGAF thread. The post was made by a user called Stinkles (who has been verified as O'Connor). If correct, then Halo 5 sold astonishingly well during the first few months of release, probably enough to beat nearly all other exclusives across both PS4 and Xbox One last year. We'll no doubt get an update from either O'Connor himself or someone at Microsoft; and when we do we'll keep you posted.