https://wccftech.com/animal-crossing-new-horizons-1-1-1-duplication/

A new Animal Crossing: New Horizons update has been released worldwide, and it has finally been discovered what it actually does.

According to the game's IGN Wiki, the 1.1.1 update fixes the duplication glitch. This glitch allowed players to duplicate items and sell them for huge amounts of bells, effectively damaging the game's balance.