Here’s how it works:You load up Cistern of Slaughter, the wave-clearing event with all the wild animals. If you do this five times, a red chest will become unlocked in the back of the arena. A red chest, which, because of this event, is going to probably have a bunch of legendaries in it. If you start the game too fast the hotfix won’t be there and the chest event won’t get active. Chance are that this glitch has always existed, but red chest drop rates have been so terrible before this event there was no reason to run it.

Source: Forbes February 01, 2020 14:15 UTC