Discover Financial Services – 16.8% Stock was down 16.5% at $101.61 recently after the company revealed an investigation by Federal Deposit Insurance Corp. Dow Jones Market Data says the stock is on track to suffer its biggest single-day decline since March 18, 2020 when it fell by 26.7%. Discover Financial said it also booked a 365 million liability for refunds to merchants following a misclassification. Discover Financial stated that it was “difficult” to determine the amount of refunds due at this time. Discover Financial Services, the worst performing stock in the S&P500 SPX -0.62% is ending a three-day streak of winning. The stock has still gained more than 6% in 2023.