Critical x402 SDK flaw let malicious APIs drain AI agents' token balances

Security firm V12 said on October 22 that the x402 SDKs' default client set no spending limit, so a malicious API could request a signature for an AI agent's entire balance of a supported token. A limit was added only in releases from August 18, and the risk affected agents that signed payments automatically.

• x402 SDK default client set no spending limit
• Malicious API could obtain a signature for the full token balance
• Spending limit appeared only in SDK releases from August 18
• Risk affected agents that signed payments automatically