GoPlus: Bitget’s $387.5M Hack Exploited the…

GoPlus Security has concluded that the $387.5 million Bitget breach stemmed from a compromise of the exchange's transaction-signing "trust chain" rather than the theft of private keys. According to the security firm's analysis of the September 24 incident, attackers penetrated a critical wallet backend system, forged transaction data, and induced Bitget's authorization process to produce cryptographically valid signatures for transfers the exchange had never intended to approve. In effect, the signing keys behaved exactly as designed — the information they were asked to sign had already been manipulated.

Bitget has separately stated that its private keys were not stolen and that it has identified and fixed the underlying vulnerability, though a full technical post-mortem has not yet been published.

Timeline and scope of the drain

Bitget detected unauthorized transfers at 18:31 UTC on September 24 and initially put the impact at roughly $351.6 million. Onchain tracing later lifted the total to $387.5 million after transfers involving Zcash and TRON were folded into the accounting; Bitget said the revision reflected more complete bookkeeping rather than further theft. Assets involved included XRP, ETH, USDT, ZEC, USDC, USDT0, XAUt, BNB, AVAX and TRX, spanning Ethereum and other EVM networks, XRP Ledger, Zcash and TRON. GoPlus estimates the main drain lasted about two hours and 25 minutes, with the largest single wave moving roughly $185 million in about one minute — a timeline that raises questions about why automated controls did not stop subsequent transfers once abnormal activity began.

Bitget halted withdrawals after the incident while keeping deposits and trading live, and said cold wallets and customer balances were untouched. Its self-custodial Bitget Wallet product was unaffected because it runs on separate infrastructure.

Why signing security is drawing scrutiny

GoPlus argues that the distinction between stealing keys and subverting the signing pipeline matters a great deal. Custody systems typically protect keys with hardware security modules, cold storage and multi-party approvals, but those defenses weaken if an attacker can control the data reaching an otherwise secure signer. A valid signature proves that an authorized key approved specific transaction data; it does not prove the request itself was legitimate. The firm recommends independent pre-signing controls that verify destinations, amounts and transaction context instead of relying on one upstream source of trusted information. It also drew structural parallels to the $1.5 billion Bybit hack of February 2025, noting that both attacks targeted trust around the signing process even though the mechanisms differed.

GoPlus has blacklisted addresses tied to the Bitget attacker and shared them with ecosystem partners. Bitget is investigating alongside Mandiant and SlowMist, has notified law enforcement and has launched a recovery bounty. The exchange said its User Protection Fund held more than $464 million at the time of the incident, above the revised loss figure. The attackers' initial point of entry and the exact backend component compromised remain under forensic review.