A critical security alert has been issued for the x402 cross-chain protocol (@402bridge) following a confirmed exploit that resulted in the theft of 17,693 USDC from over 200 users. The security incident, flagged by the GoPlus Chinese community, reveals a sophisticated attack vector involving contract ownership transfer and authorization abuse.
Attack Vector Analysis
The exploit began when the original contract creator (0xed1A) transferred ownership to address 0x2b8F. The new owner then utilized the transferUserToken method within the contract to systematically drain remaining USDC balances from all authorized user wallets. The attack was possible because users had previously granted unlimited USDC authorization to the @402bridge contract during minting operations.
Fund Movement and Laundering
Following the theft, the attacker converted the stolen 17,693 USDC to Ethereum and initiated multiple cross-chain transactions to Arbitrum, a common technique used to obscure fund trails and complicate recovery efforts. The cross-chain movement suggests sophisticated operational security by the attacker.
User Protection Recommendations
Security experts recommend immediate action for affected users:
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Revoke all authorizations to the x402 protocol immediately
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Verify authorization addresses against official project sources before granting permissions
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Implement minimum necessary authorization amounts instead of unlimited approvals
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Conduct regular authorization audits and remove unnecessary permissions
Broader Security Implications
This incident highlights the critical risks associated with unlimited token approvals in DeFi protocols. The attack demonstrates how contract ownership changes can transform previously trusted protocols into security threats, emphasizing the need for continuous monitoring of DeFi interactions even after initial authorization.
The x402 protocol team has not yet issued an official statement regarding the exploit or potential compensation for affected users, leaving community security groups as the primary source of warning and guidance.