Version 1.20.1 Forge (47.3.33)

While the trade gui is open, putting any stackable item in the top left corner of player inventory and then shift-clicking it will cause it to move to 9th slot of player hotbar and dupe.
This works on server and singleplayer. I didn't use any other mods than mowzies mobs and geckolib.
Here is a footage of me performing the dupe:
https://youtu.be/fI3vT0SF6hE

Woahhh that's bad!
If you reload the game are the items still there?

Yes the items stay duped in my inventory after reloading the game. They also stay in the inventory on multiplayer, even after rejoining, using /reload on the server and even turning the server on and off.

Woahhh that's bad! If you reload the game are the items still there?

Sorry for hijacking, do you plan to release a new build on curseforge with the fixes to bluffs?

@oguh43 I'm unaware of any issues with Bluffs. Please report the issue in a separate post.

@oguh43 I'm unaware of any issues with Bluffs. Please report the issue in a separate post.

#826 you fixed it in 944dcde but made no new release on curseforge, thus the newest available version still corrupts worlds

Oh! The release will come when I fix all of the current bugs.