There are claims that the real authors of the gospels are unknown - that they are anonymous. The suspicion is that the Christians later added the titles (Matthew, Mark, Luke and John). This suspicion is unfounded, since the earliest manuscripts in existence (not far removed from the originals) have the titles on them. In this case, the burden of proof lies with the claimants. Finding at least one copy (preferably more, since copyist omissions can happen) of a manuscript without the title would be a start, but again, secular, anti-Biblical preferences show through and suggestions are given the credence of conclusive evidence. " 'Tain't fair," says I.
We should keep in mind the historical way the gospels and indeed, the entire New Testament came about. There is an unbroken chain of custody of the material written by the Apostles and their direct students (the requirement for authoritative canon, of which the Christian community was well aware). The official canon declaration at Nicea, in AD 325 was a formality only. I still wait for someone to explain to me how a forger could have snuck his material into acceptance by foundational or subsequent Christian leadership and community. Why was the work of the Apostles accepted? They were empowered by the Holy Spirit, which Jesus sent to work miracles and speak with power. No wonder written work was not accepted from just anyone.