NFT marketplace OpenSea is investigating a phishing hack

OpenSea CEO Devin Finzer said the hacker "has $1.7 million of ETH in his wallet from selling some of the stolen NFTs."

NFT marketplace OpenSea is investigating a phishing hack

A smartphone and a screen show the website OpenSea, where digital artworks are sold using NFT. NFTs, non-fungible tokens, are unique cryptographic credentials that are written to the blockchain attached to a file (image, music, video).

picture alliance | picture alliance | Getty Images

NFT marketplace OpenSea is investigating a "phishing attack" that no longer appears to be active, the company's chief executive said late Saturday.

"We don't believe it's connected to the OpenSea website. It appears 32 users thus far have signed a malicious payload from an attacker, and some of their NFTs were stolen," Devin Finzer said on Twitter. NFTs, or non-fungible tokens, have surged in popularity over the past year.

Ownership of these assets is recorded on a blockchain — a digital ledger similar to the networks that underpin bitcoin and other cryptocurrencies. Unlike most currencies, however, a person can't exchange one NFT for another as they would with dollars or other assets. Each NFT is unique and acts as a collector's item that can't be duplicated, making them rare by design.

Some of the stolen NFTs have been returned, Finzer said.

In a series of tweets, Finzer dispelled rumors that the hack was worth $200 million. Finzer said the hacker "has $1.7 million of ETH in his wallet from selling some of the stolen NFTs."

Subscribe to CNBC on YouTube.