Square Art in Web 4.155.0

Plex Media Server
1

Server Version#: 1.43.0.10346

Where do the squareArt images available in Web 4.155.0 come from?

I’ve done a couple myself editing and cropping 16:9 background images but can’t find square art in TMDB or TvDB

Does anybody know where Plex sources it's Square Art from?