Shares of Valeant Pharmaceuticals popped 4.4 percent Monday after short-seller Andrew Left said he was long the stock.
Left, executive editor of Citron Research, confirmed to CNBC that while he has out-of-the-money puts on the stock, he is long the embattled pharmaceutical company. The position means that Left could potentially make some money on the trade whether the stock rises or falls.
It's a dramatic about-face for Left, who in October sent the stock sliding after he likened it to Enron.
[Programming note: Left will be on CNBC's "Fast Money: Halftime Report," Tuesday in an exclusive interview.]
TheStreet.com initially reported Left's position, which broke in a Monday interview with Real Money. Left told TheStreet.com that he "wouldn't be surprised if there's a bounce" in Valeant, though he also said he didn't think Valeant "would make any decisions that are going to torpedo their company."
Valeant has been the target of regulatory probes on its pricing, inventory and accounting practices, drawing the ire of investors like Berkshire Hathaway Vice Chairman Charlie Munger, who called it a "sewer." Shares of Valeant have fallen nearly 90 percent over the past 12 months.
"We are generating cash, we are generating EBITDA, we've got over $10 billion of sales," New CEO Joseph Papa told CNBC's Jim Cramer last week. "So, I do think the footprint is in place."
Valeant moved higher on a day a fund that tracks the biotechnology sector rose 3 percent, its best day since April 21.
— Reporting by CNBC's Patty Martell and Alex Crippen. Abigail Stevenson contributed to this report.