If you thought that only proof of work coins were susceptible to double spending attacks, you haven’t met tether. The world’s ninth largest crypto by market cap and second largest by volume is meant to be a haven in a sea of uncertainty, but even it’s not immune to jiggery-pokery, as we’ll learn in today’s Bitcoin in Brief.

How to Have Your Dollar Peg and Spend It

If you were told that another cryptocurrency had been double spent, you’d probably guess it was a low hashrate PoW coin, not USDT. By rights, it ought to be impossible to double spend tether, but that’s what happened on June 28 according to one Chinese cybersecurity firm. Someone sent 694 tether to an exchange and was credited for the deposit due to a certain field value pertaining to the transaction being altered. An Omni dev (whose blockchain tether operates on) has since confirmed this did occur, but was the fault of the exchange for poor integration, rather than a flaw in tether itself. Still, the news has prompted at least one exchange, Okex, to issue reassurances that its exchange is safe from this bug.

Tether’s most prominent critics have long asserted that the company doesn’t have enough US dollars in the bank to cover the amount of USDT in circulation. If rampant double spending starts to occur, they’ll be right.