Duplication anything with player duplication

[GedeonGrays]

Hello o/

Crucible Version: 4.1 (version with fix a written book by juanmuscaria in Discord)

This seems to be a fairly old problem that is present on any server core and on almost any version of Minecraft, according to the official Mojang bug tracker: https://bugs.mojang.com/browse/MC-37586

How duplication works:

All we need to do is go to the server under the same account several times. You can duplicate everything that is put into inventory, since the inventory is one for all versions of your account. For clarity, in the video below, one of my friends uses an account named KAIIIAK and only this one.

How to reproduce duplication:

You can check the timecodes (TC) from the video. Link: https://youtu.be/_ojJGIuwKXg

Note: since it can be difficult to understand which of the clients connecting to the server under one account I mean at a particular moment, let's call the client on the left “LEFT” and the client on the right, respectively, “RIGHT”.

1. First of all, LEFT connected to the server to select duplicate items (TC). Leaves the server. RIGHT connected to the server to show that this is the same account (TC). Leaves the server.
2. Now we need to start the Windows Task Manager, go to the Performance tab and open the Resource Monitor. In the list of processes that appears, you need to find the process of the selected client. In our case, this is the second javaw.exe, which belongs to the RIGHT. Then we right-click on our process and select the Suspend Process (TC). As we can see, RIGHT is no longer active.
3. Next, RIGHT simply connects to the server, but suspends the process at the last stage of the connection (TC).
4. Then, when LEFT connects to the server again, we go to the RIGHT process and click Resume Process (TC). As we again see, now on the server there are two versions of the same KAIIIAK account (for some reason, the server adds random numbers to the nickname each time it reconnects, but this is still the same account).
5. Finally, we simply shift all duplicate items from both inventories of the same account (TC).

[juanmuscaria]

Not the ideal fix, but having a plugin to listen to player pre login event and cancel the login in case the player is already logged in the server wold prevent that from happening, wouldn't it? If it becomes a real problem for your server using a plugin is an option while we try to fix this issue.

[GedeonGrays]

I think that for me personally this is not so critical, although the problem is quite serious, given the ease of execution on any server. In general, I will wait for a fix at any time.