Item Dupe

There exists an Item dupe glitch caused by the processing of packets after a client has been kicked.

To replicate this you must first gather at least 1 of the material you wish to duplicate. Place it in the first slot and have it selected.

The second part requires to quick sending of two consecutive packets.
The first packet is Packet3Chat that contains a '/' and and Illegal Character.
The second packet is Packet14BlockDig. This only needs the status field set to either 3 or 4.

This works because the chat packet causes the player to be disconnected because of invalid chat characters. This causes the players inventory to be saved.

The problem lies in what happens next. The main thread continues to process any remaining packets which includes the Packet14BlockDig packet. This causes the currently held item to be dropped but the player is never saved out again. After logging back in your inventory will remain the same and your duped item will be floating in front of you.