George Soros speaking at the 2015 CGI Annual Meeting in New York.

George Soros' investment fund has bought a large amount of stock in Overstock.com, a company that has seen its share price surge after announcing a cryptocurrency trading product.

Soros Fund Management held 2,472,188 shares in Overstock at the end of the fourth quarter of 2017, making it the third-largest shareholder, according to regulatory filings released late Wednesday.

These were worth $157.97 million at the end of the last trading day in December and $146.72 million at the close of trade Wednesday.

Shares of Overstock have risen over 200 percent in the last year after the company announced plans to jump into the digital coin-trading business in September. Overstock's majority-owned subsidiary tZero teamed up with two financial services companies, RenGen and Argon, to create what they call a "distributed ledger platform for capital markets."

Overstock is an e-commerce firm focused on home goods and clothes. Chief Executive Patrick Byrne has been bullish on bitcoin, which it has accepted as payment since 2014, and the technology that underpins it, known as blockchain.

The Securities and Exchange Commission (SEC) filings do not give any commentary behind what stocks funds buy and sell.

Soros spoke publicly about the cryptocurrency space in January at the World Economic Forum (WEF) in Davos, Switzerland. The billionaire investor said that blockchain technology could be put to "positive use," but cryptocurrency is a "typical bubble."