Binance Smart Chain, the relatively popular blockchain that Binance is trying to rebrand as « BNB Chain », was halted when an attacker exploited « BSC Token Hub », the bridge between the old Binance Beacon Chain and BSC. The attacker successfully moved around $127 million of the stolen crypto assets off the chain before it was paused. The attacker’s wallet contained 2 million BNB, valued at $586 million based on the price at the time of the hack, but as a result of the chain halt, they were not able to exfiltrate the entire amount.
Binance CEO Changpeng Zhao (« CZ ») tweeted that « An exploit on a cross-chain bridge, BSC Token Hub, resulted in extra BNB. We have asked all validators to temporarily suspend BSC. » A BSC developer later confirmed that « we coordinated with validators to temporarily suspend BSC after having determined an exploit on a cross-chain bridge, BSC Token Hub- which resulted in extra BNB ». The value of the $BNB token dropped from $293.10 to $280.40 after the news.
The chain operators and CZ seemed to feel a little awkward about the ramifications of unilaterally deciding to halt a supposedly decentralized blockchain. CZ claimed he was asleep and that the chain had already been halted by the time he woke up. The BSC team published a blog post saying that « Decentralized chains are not designed to be stopped, but by contacting community validators one by one, we were able to stop the incident from spreading. It was not that easy as BNB Smart Chain has 26 active validators at present and 44 in total in different time zones. This delayed closure, but we were able to minimize the loss. » They also promised to try to decentralize the project even further going forward.