This leak is not normal from the game files, it came directly from the source itself.
In the official Instagram post for Fortnite Game, the company accidentally published a photo of a previously unseen skin.
Blue elf with ice wings on the back, the skin looks pretty clean. Here is a screenshot of the quickly deleted history:
This topic is likely to be published the next day, but now in Epic there is definitely a manager for social networks in hot water.