The Testimonium Flavianum (Antiquities 18.63) was interpolated by a Christian, but most scholars think an authentic Josephus reference to Jesus underlies it

Most scholars believe the Testimonium Flavianum was doctored by a Christian editor, possibly in the 2nd or 3rd century, adding affirmations like "he was certainly the Messiah" and "he rose from the dead." Evidence: Origen reports Josephus was not a Christian. However, the text fits contextually, so most Josephus scholars believe an original, toned-down reference to Jesus exists there.