Short Sellers Bet Tether, Crypto’s Central Bank, Is Vulnerable to a Run

Short sellers are betting against a cryptocurrency whose price shouldn’t move.

A few investment firms, including Fir Tree Partners and Viceroy Research LLC, have placed substantial bets in recent months that the price of tether will fall, according to people familiar with the matter. Tether is the most popular currency for trading bitcoin and is supposed to have a fixed value pegged to the U.S. dollar.