Server can use level:// resource pack URI

The bug

The method net.minecraft.client.multiplayer.ClientPacketListener.handleResourcePack(ClientboundResourcePackPacket) (20w07a Mojang name) allows remote servers to use the custom URI scheme level. This scheme is intended for clients connecting to the integrated server started by the same Minecraft instance.
This allows the remote server to detect which world folders containing a resources.zip the player has.