Whitehat developer unlocks $2 million trapped in 2016 Ethereum ICO

A security researcher known as 0xflorent worked with the team behind the 2016 HongCoin token sale to unlock about 1,003.62 ETH — roughly $2 million — that had been trapped for nine years. The coordinated whitehat recovery made 48 original investors eligible to claim their refunds; two have retrieved a combined 96.5 ETH, he said in an X thread Sunday.

The HongCoin contract's refund function failed because a global counter, reduced by years of partial refunds, fell to 356 and capped refunds at 3.56 ETH. An admin function, restricted to the project's multisig, lacked integer-overflow protections. Calling that function with a specific input reset a holder's balance to one, allowing the refund check to pass and release the funds.

The recovery required the multisig's participation. 0xflorent contacted the team, validated the unlock on a test fork of Ethereum's mainnet, and the team signed the unlock transactions.

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