#1 Drop an item either on the roof/ground floor/next to a wall in a building.

#2 Stand directly above/below/beside the item depending where you dropped it.

#3 Open the inventory and pick up the item using the vicinity window.

Looting through walls is a minor issue, as both you and the item have to be very close to the wall in order for it to work, but for ceilings/floors it's a much bigger issue as it seems to always work regardless of distance, essentially letting you loot the roof of a building from the ground floor, providing you are standing directly beneath the items.

From what I have tested, this works on all servers, all buildings and with every item in the game.

Version 0.63.147219