On November 19, 2017, $30.95M USDT was removed from Tether's Treasury wallet and sent to an unauthorized address. Tether blocked the tokens and marked them as non-redeemable, preventing their circulation. Tether worked with the Omni Foundation to implement protocol upgrades allowing eventual token reclamation.

Tether, the issuer of USDT, issued a statement stating that its system was hacked by an external attacker on the 19th of this month and stolen USDT tokens worth approximately $31 million from its Tether Treasury wallet.