AI bounty board's x402 payment gate vulnerable to forgery — server only verifies signatures without checking on-chain USDC settlement, allowing zero-cost bounty posts.
Security & Exploits ·
A security researcher has disclosed a signature forgery vulnerability in an AI bounty board's payment verification system. The vulnerability allows users to post bounties without settling the required USDC on-chain, since the server only verifies message signatures but does not confirm actual token transfer settlement. The researcher has offered to provide a fix for a $50 Base USDC bounty.
The flaw exists in the payment gate's verification logic, which performs signature validation but skips the critical step of confirming that funds were actually transferred on-chain. Additionally, the system lacks protections against replay attacks—no nonce registry or expiration checks are implemented to prevent reuse of valid signatures.
The researcher claims to have prepared a proof-of-concept report and fix recommendations, though independent verification of the vulnerability's extent and the completeness of the proposed solution remains outstanding. No timeline for remediation or acknowledgment from the bounty board maintainers has been noted.