The furnace can duplicate any item

Any item can be duplicated by a furnace (or a blast furnace or a smoker).

The duplicated items can be crafted and placed.

*This bug needs to use a controller or touch.

The bug can be exploited on multiplayer servers and is difficult to detect if it is abused by other players.

The game experience of Minecraft is severely impacted by this.

*This bug was discovered by the Japanese YouTube community, not my discovery.

 

Steps to Reproduce:

Smeltable Items

1. Prepare 64 stackable items you don't need, such as dirt.
2. Smelt items in the furnace.
3. Choose the output slot in the furnace interface.
4. Mash the unneeded items in your inventory (press a button or tap repeatedly).
5. Collect the items in the output slot.

Unsmeltable Items

1. Step 1 -4 of the steps in smeltable items.
2. Close the furnace interface.
3. Open the furnace interface.
4. Select the output slot on the furnace interface.
5. Mash the unneeded item in your inventory.
6. Collect the items in the output slot.