Somewhere in Blizzard HQ, a janitor is presumably sweeping up shards of glass after someone on the Diablo 4 development team finally had good reason to slam the big red button in a case labeled "in case of emergency, break glass." Blizzard has temporarily disabled trading in Diablo 4 on the heels of a Season 5 exploit that flooded the in-game economy with countless duped items.
Community manager Adam "PezRadar" Fletcher confirmed Blizzard's response in a forum post earlier today: "We will be disabling trading in Diablo IV while we investigate a possible duplication issue. We apologize for the disruption and will provide updates on when we will have trading available again once we further investigate and identify any issues we need to resolve."
As Diablo fiend Rob2628 noted, the dupe seems to have been highlighted in a livestream held by Chinese players on video site bilibili, though it's currently unclear whether the dupe actually originated in China. Screenshots of inventories and marketplaces flooded with countless stacks of normally scarce items have cropped up online, supporting the theory that the dupe could be applied to any stackable item.
Season 5 has been well received by players, but it's also been a curiously buggy experience. Diablo 4 accidentally gave players a bunch of extra tempering recipes right at the start, but Blizzard decided it was too fun to fix and is "letting this one slide." However, the devs were quick to stamp out an XP bug tied to a new Unique which was unintentionally dishing out millions of XP at a time.