I was trading on the ORAS GTS and someone offered me a level 61 shiny Xerneas in a Master Ball. It was met on 3/18/2016 at Team Flare Secret HQ, met at level 50. I was wondering if it was hacked, because I believe the Xerneas in XY is shiny locked.
Yes, of course it's hacked. Xerneas is shiny locked in X/Y, and that Xerneas wasn't caught during any of the shiny Xerneas events, as far as I can tell.