The ability of Tether’s USDT stablecoin to maintain its peg to the US dollar has been downgraded to the lowest rating by S&P Global Ratings, which warned that a drop in Bitcoin’s value could leave the stablecoin undercollateralized.The token was awarded a stability rating of “weak” by analysts at the ratings firm on Wednesday, down from “constrained” previously. S&P said its assessment “reflects the rise in exposure to high-risk assets in USDT’s reserves over the past year,” including Bitcoin, g...