Circle's stock has fallen, with reports citing the launch of a new rival stablecoin that targets the enterprise users of USDC. The new stablecoin, Open USD, is backed by Visa and is part of the company's stablecoin platform for banks and fintechs. However, the extent of the stock's decline is unclear, with different reports stating it fell by 15% or 18%, and one report even indicating a pre-market climb.