It has been a pretty short sigh of relief since the famous Luminose City glitch on Pokemon X and Y get fixed before a number of new glitches and corrupted saves reveals themselves.
Another glitch has been recently reported by the game’s official Facebook page administrators where it affects most players who are active in Wonder Trade. It appears that a player might get a Mystery Egg from a smooth trade. During the process, a flawed Pokemon will corrupt the egg and takes it place thus transforming what is referred to a Mystery Egg.
The Mystery Egg can pose quite a problem to every player. Apparently, it can multiply and corrupts the PC box along with every Pokemon in that box. These eggs can appear out of nowhere without prior warning. There is even a video uploaded demonstrating the glitch on the Facebook page.
Other known features of the Egg is that you simply can’t discard it or even hatch it. The only solution at the moment is simply prevention. Avoid taking the Mystery Egg. If you just received one, put it in a separate box away from all your Pokemon. If a Pokemon already shared the same box, separate it also from the others to prevent any unnecessary outbreak.
So far that is all the information we have on the glitch. Please avoid the Egg. Apparently prevention is the only solution.