OpenSea users received phishing emails impersonating the platform and requesting wallet connection for a contract migration. Attackers tricked users into approving malicious transactions that transferred NFTs to attacker-controlled wallets. The attack stole approximately 640 ETH worth of NFTs from 28 wallets.

According to OpenSea's official tweet, hackers sent phishing emails to all users' mailboxes at the same time as the OpenSea contract was upgraded. Many users mistakenly thought it was an official email and authorized the wallet, which resulted in the wallet being stolen. OpenSea co-founder and CEO Devin Finzer confirmed the phishing attack in a tweet.