In a dramatic twist, one of this week’s Multichain hackers has returned 322 ETH ($974,000 at the time of writing) to the cross-chain router protocol and one of the affected users.
However the hacker kept 62 ETH ($187,000) as a “bug bounty”, and a total of 528 ETH (worth $1.6M) remains outstanding after the exploits.
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Earlier this week, news emerged of a security vulnerability with Multichain relating to the tokens WETH, PERI, OMT, WBNB, MATIC, and AVAX, and $1.43 million was stolen. Multichain announced on Jan. 17 the critical vulnerability had been “reported and fixed.”
However, publicity about the vulnerability reportedly encouraged a number of different attackers to swoop in, and more than $3 million in funds were stolen. The critical vulnerability in the six tokens still exists, but Multichain has drained around $44.5m of funds from multiple chain bridges to protect them.
One of the hackers, calling himself a "white hat" has been in communication with both Multichain and a user who lost $960,000 in the past day or so, to negotiate returning 80% of the money in return for a hefty finders fee.
According to a Jan. 20 tweet from ZenGo wallet co-founder Tal Be’ery, the hacker claimed they hadbeen “saving the rest” of the Multichain users who were being targeted by bots, in an act of defensive hacking.
The funds were returned across four transactions. On Jan. 20 the hacker returned 269 ETH ($813,000) in two transactions directly to the user he stole it from and kept a bug bounty of 50 ETH ($150,000).
The relieved user responded to the hacker:
“Well received, thank you for your honesty.”
Overnight, the hacker also returned 50 ETH ($150,000) across two transactions to the official Multichain address, and kept a bug bounty of 12 ETH ($36,000).
Related: Multichain asks users to revoke approvals amid ‘critical vulnerability’
Multichain (formerly Anyswap) aims to be the “ultimate router for Web3.” The platform supports 30 chains at the moment, including Bitcoin (BTC), Ethereum (ETH), Avalanche (AVAX), Litecoin (LTC), Terra (LUNA), and Fantom (FTM).
In a tweet on Jan. 20, the Co-Founder and CEO of Multichain Zhaojun conceded that Multichain bridge contracts need a pause function to deal with similar incidents in future..
Cointelegraph has contacted the project for comment.
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