https://www.vice.com/en_us/article/xgd53z/hacker-actively-stealing-high-value-nfts-on-opensea

A hacker or hackers are actively stealing and flipping high-valued NFTs from users on OpenSea, the world’s largest NFT exchange, causing chaos and confusion in the broader NFT community.

The current mechanism for the hack is currently unknown, but OpenSea placed a red banner at the top of its site Saturday night saying “We are actively investigating rumors of an exploit associated with OpenSea related smart contracts. This appears to be a phishing attack originating outside of OpenSea's website. Do not click links outside of opensea.io.”