Binance, the world's largest cryptocurrency exchange by trading volume, halted withdrawals of ankr ( ANKR-USD ) coins after a private key, a sort of password that allows users to access their funds, got hacked, the company's CEO wrote in a Twitter post Friday. "Initial analysis is developer private key was hacked, and the hacker updated the smart contract to a more malicious one," Changpeng Zhao explained, adding that Binance froze about $3M that hackers moved to its centralized exchange (CEX). Ankr said it told decentralized exchanges (DEXes) to block trading and noted it will re-issue tokens after the exploit has been assessed. ANKR tokens slipped 3.4% to two cents in Friday morning trading, down from its April peak of around $0.18. The cryptoverse has been stung by a slew of high-profile blockchain attacks in recent months. For instance, Binance temporarily halted its blockchain network on October 7 after an attacker stole 2M of its BNB tokens.