Avis Takes Aim at Hedge Fund Pentwater for Stock Boom, Bust

Avis Budget Group Inc.’s chief executive officer lashed out at one of the car-rental company’s biggest investors, claiming it likely triggered the steep stock-price plunge last week and may have run afoul of Securities and Exchange Commission rules in the process.

The firm, Pentwater Capital Management LP, initially helped to fuel a massive rally with its disclosure that it had amassed a big stake in the company. That sent short-sellers racing to buy the stock to close out bearish bets, pushing the price up by more than 600% in a few weeks.