The vulnerability of the OpenSea marketplace allowed one of the buyers to purchase NFT from the Bored Ape Yacht Club (BAYC) collection ten times lower than their current price.
The ex-owner of BAYC #9991 announced on Twitter that his NFT was sold for just 0.77 ETH ($1,700), while the minimum price of one NFT from the collection is now 86 ETH ($200,000).
Similarly, BAYC #8924 was sold for 6.66 ETH ($14,700) and BAYC #8924 for 23 ETH ($50,800). In addition, the buyer under the nickname "Jpegdegenlove" managed to purchase two NFT Mutant Apes, one NFT Cool Cats and one NFT CyberKongz. Thus, he gained at least 332 ETH ($733,000). In the case of BAYC for 23 ETH, Jpegdegenlove was able to resell it for 135 ETH, quickly making over 100 ETH profit.
During the analysis of the situation, it turned out that these NFTs were not completely withdrawn from sale on OpenSea. Instead, the holders used a trick to remove the NFT from the OpenSea interface by transferring it to a third-party wallet and then returning it to the main one. This helps to avoid delisting fees. Nevertheless, this approach does not cancel the part concerning the offer to sell NFTs in the blockchain, which is why they remain vulnerable to an exploit through the marketplace API.
"If you have active listings that have not been canceled and have not reached the expiration date, they still exist," OpenSea confirmed.
To check the availability of such tokens in the wallet, users are invited to use the service orders.rarible.com, which displays current and old listings on Raible and OpenSea. After that, you can completely withdraw the NFT from sale by conducting a transaction with the payment of the appropriate commission. The service was launched at the beginning of the month for such cases, after NFT Mutant Serum was sold for 11.55 ETH on January 5 at a minimum price of 32 ETH. The first cases of using the exploit were noticed at the end of December.
"The thief uses a bot that scans the blockchain in search of pending transactions with a price below the current minimum, and buys NFT," explained the administrator of the NFT project Joe Vargas.