Bill Ackman went on the attack against Herbalife today--and shares surged upward.
At the Robin Hood Investors Conference, Ackman said in an interview that he would take his campaign against the company "to the end of the earth."
At an investor conference last year, Ackman announced that he was shorting Herbalife's stock. He described the company as a "pyramid scheme." Other investors, including Carl Icahn and George Soros, subsequently bought large stakes in Herbalife.
(Read more: Short sellers see big chance-if they can survive)
Shares moved higher even as Ackman, the founder of the Pershing Square hedge fund, was speaking.
Adding to the irony, shares of JC Penney, a company Ackman once had a large position in, sank in morning trading. Ackman reportedly said at Robin Hood that he hopes JC Penney does well.
—By CNBC's John Carney. Follow him on Twitter @Carney