Avis has accused Florida‑based Pentwater Capital Management of driving a sharp, short‑squeeze that lifted the rental‑car stock from under $150 to about $848 before a quick reversal.

Pentwater was the only major investor active during the run‑up, and Avis CEO Brian Choi warned that a short‑swing profit rule could force the firm to return gains from recent sales.

Pentwater’s filings show 94,000 of the 4.3 million shares sold last week fall under the rule. The hedge fund has said it will collaborate with Avis and voluntarily hand over any profits from those shares.

The episode highlights how regulatory safeguards can intersect with volatile trading, potentially affecting shareholder returns and market stability for a high‑profile mid‑cap name.