Map center coordinates are sent to players

I believe that filled maps send the map data's center X/Z coordinates, after I decompiled the game to see if banners in maps leak coords in the map item. This suspicion came after a griefer group managed to grief high-security bases and they claimed they did it "using only maps".

In Yarn mappings, FilledMapItem doesn't filter MapState.xCenter and zCenter when it is createSyncPacket()ing, or in any of its steps, never mind NetworkSyncedItem or ServerPlayerEntity.playerTick().