11/11 Dupe

The 11/11 Dupe, also known as the Drop Dupe, was an infamous duplication glitch that occurred on November 11, 2016.

One of the major glitches in 2b2t history, it occurred when RusherIsAutistic leaked an easy way to duplicate items, causing mass duping across the entire server. Many players who abused this glitch used it to duplicate double chests worth of enchanted apples and other rare items, crashing the 2b2t economy.

Glitch
The glitch involved dropping an item and instantly disconnecting from the server. When logging back in, the item would be both on the ground and in the player's inventory. At the time, it was the largest duplication glitch on the server, since an entire inventory worth of items could be duplicated at once.

Another method of duping was found by the 4th Reich; the 4th Reich employed a method that used two Minecraft windows, one for joining in the server, and the other for dropping the item.

The infamous trader kinorana created a client to easily perform the glitch. The client, kinodupe, had the capability of duping an entire inventory worth of items at once. The client was backdoored, however, and people who duped using the client had their stashes leaked on the 2b2t subreddit. Cheat clients such as Impact and Wurst were soon updated to add features capable of performing the glitch.

Aftermath
The glitch was patched on November 28, 2016, when the server updated to 1.11.