Vulnerability / research

x402 research exposes payment bypass, login relay and wallet-drain risks

Reported

Published here

What happened

V12 found flaws in x402 agent-payment software that could authorize an entire supported token balance, sign a login challenge for another site, or accept a Solana token approval as payment.

Parties and reporting

AI tools and systems: x402 client SDKs, TypeScript Solana payment facilitators, Sign-In-With-X extension, Automatic wallet signers

Outcome

V12 says the three critical findings were fixed by August 20 after private disclosure on August 12. Its October 22 report describes local tests; no real-world theft is established.

Operating lesson

Enforce payment and total budgets before signing, bind login signatures to the contacted site, and verify that settlement actually transfers the required funds.

Evidence and limits

Research, not an observed attack. The payment-bypass test did not submit a live transaction; session takeover and wallet draining are conditional impacts. August dates concern private reporting and fixes, not this public research disclosure. Fixed versions are not named in the primary report.

Sources