x402 SDK Flaws Put AI Agent Wallets at Risk

V12 found 25 flaws in the x402 SDKs, including three critical issues, reports The Hacker News. The x402 Foundation fixed all three critical flaws in releases published on August 18.

Before the fixes, the default client had no spending limit. A malicious API could request an agent's full balance of a supported token, and an agent configured to sign payments automatically could approve the transfer. Updated TypeScript, Python and Go clients now limit each payment to $1 by default and allow only recognized US dollar stablecoins.

A separate TypeScript flaw allowed a Solana facilitator to accept a transaction that moved no tokens as valid payment. Another issue could make an agent sign a login message for a different website. No attacks using the flaws have been publicly reported, but the foundation did not publish a security advisory, and package vulnerability checks did not warn users of the affected releases.