402Bridge Exploited for $17K in Private Key Leak Amid x402 Trend

PeckShieldAlert has reported a security incident affecting 402Bridge, resulting in the theft of approximately $17,000 worth of USDC. The breach impacted over 200 users and occurred just days after the project's launch and the growing popularity of its x402 payment protocol.

The incident quickly garnered attention within the cryptocurrency community, with security firms advising users to revoke any active authorizations connected to the compromised address. PeckShieldAlert stated in an X post, "#PeckShieldAlert @402bridge has been exploited. ~17K $USDC was stolen. Please *Revoke* your allowance, if any, to 0xed1AFc4DCfb39b9ab9d67f3f7f7d02803cEA9FC5."

Private Key Exposure Identified as Exploit Cause

The team behind 402Bridge attributed the attack to a significant design vulnerability in their backend operations. They explained that the x402 mechanism requires users to sign or approve transactions through the web interface, which are then processed by a backend server. This server utilizes an admin private key to execute contract methods. When this server is connected to the internet, it inadvertently exposes administrative privileges.

This configuration is believed to have enabled hackers to gain access to the private key and subsequently reroute user funds. According to Cos, founder of Slowmist, the hacker's wallet address, 0x2b8F, acquired approximately $17,693 in USDC. This amount was then converted into 4.2 ETH. The hacker proceeded to transfer the stolen ETH to Arbitrum through a series of transactions, making recovery of the funds extremely challenging.

Security Alerts Issued and Industry Reactions

Following the exploit, web3 security firm GoPlus Security issued a warning to users, advising them to cancel any outstanding approvals associated with 402Bridge. The company emphasized the importance of verifying the project's official contract addresses before authorizing any transactions. Security experts also recommended that users limit the amounts they approve and regularly review their wallet permissions to enhance security.

The x402 protocol had recently gained significant attention for enabling instant payments via the HTTP 402 system. In the week leading up to October 20, 2025, the protocol processed over 932,000 transactions, indicating substantial user adoption and momentum before the security breach abruptly halted its operations.

This incident underscores the critical risks associated with inadequate private key protection. Developers are urged to implement more robust security measures for safeguarding private keys, while users should maintain vigilance by carefully reviewing transaction approvals and actively managing their wallet permissions.