When you turn up saturation then contrast it reveals a lot of little artifacts like this, but the background doesn't have any. It could be that the subject was AI generated then pasted into a clean background.
Artifacts could exist for other reasons, such as multiple lossy compressions or use of Nightshade, but I doubt either of those would leave the background clean?

I would upload a comparison image of the same process performed on my own artwork which does not create such artifacts, but my instance takes like an hour to upload an image.