Mercado Bitcoin Halts Withdrawals After Security Incident as Hypernative Flags $40M Outflows

Mercado Bitcoin, a Brazilian crypto exchange, halted deposits and withdrawals on Monday after security firm Hypernative estimated more than $40 million left exchange-linked wallets overnight. Mercado Bitcoin said it contained an early-morning incident in one of its systems and that customers suffered no losses or data leaks. Hypernative said transfers spanned at least 10 blockchains, with the largest between 6:19 and 6:53 UTC sent to newly created addresses as transactions that appeared authorized by the source wallets; it has not determined how the attacker obtained signing authority. Mercado Bitcoin later listed five destination addresses, and Tether froze USDT sent to two. Binance had also disclosed a $6.3 billion loss from hot wallets four days before, on October 29.