NFT Marketplace OpenSea Patches Flaw Potentially Leading to Cryptocurrency Theft

OpenSea, the world’s largest NFT marketplace, has addressed a security vulnerability that could have allowed hackers to hijack user accounts and empty their crypto wallets with the help of maliciously crafted NFTs (non-fungible tokens).

The issue was discovered by security researchers with Check Point, following complaints from OpenSea users of crypto-theft attempts after receiving and opening free airdropped NFTs.

NFTs are unique and non-interchangeable units of data that can be used to represent easily-reproducible items such as videos, audio and photos as unique items.

The security defect identified by Check Point could not be exploited without user interaction. The malicious NFTs would trigger pop-up messages on which the user had to accept subsequent operations that allowed hackers to grab their account information.

Specifically, the message would request for the user to allow a connection to their cryptocurrency wallet. With such pop-ups common on OpenSea for other activities, users would likely confirm the connection without too much pondering.

Thus, the victim believed they were enabling action on the received gifted NFT, but they were in fact providing the hackers with access to their wallet.

Subsequently, the hackers could initiate a fraudulent transaction from the victim’s wallet to an attacker-controlled wallet, which would trigger another pop-up message from OpenSea’s storage domain.

Should the victim accept the transaction without noticing what it was all about, their wallets would have been emptied.

It’s worth noting that the vulnerability was identified during the cybersecurity firm’s investigation into reports of wallet thefts, but this does not appear to be the flaw leveraged in those attacks.

Check Point says they informed OpenSea of the discovered security hole on September 26 and that the platform addressed the issue within an hour after receiving the report.

“These attacks would have relied on users approving malicious activity through a third-party wallet provider by connecting their wallet and providing a signature for the malicious transaction. We have been unable to identify any instances where this vulnerability was exploited,” OpenSea said.

Users are advised to carefully check all of the pop-up messages they receive and what is requested from them, to identify suspicious requests and reject them.

In August 2021, OpenSea recorded $3.4 billion in transaction volume.

Ionut Arghire is an international correspondent for SecurityWeek.

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