In December 2023, OKX's decentralized exchange (DEX) aggregator lost $2.7 million due to a private key compromise. Attackers upgraded a deprecated proxy contract and used it to siphon funds from users who had previously approved the contract. Despite community reports, OKX initially offered only partial reimbursement of $370k. This incident highlights vulnerabilities in proxy contract implementations, even with centralized entities like OKX.