A critical vulnerability in x402 SDKs could allow malicious APIs to drain AI agents' token balances, security firm V12 reported on October 22. The flaw enabled agents to sign payment requests for their entire token balance if a malicious API prompted them.
The issue stemmed from the SDKs' default client, which did not enforce spending limits. This vulnerability was addressed in releases on August 18, which introduced spending limits.
The risk primarily affected AI agents that automatically signed payments and whose applications did not have specific spending limits configured.
Sources and references
Original report
Critical x402 SDK Flaw Could Let Malicious APIs Drain AI Agents’ Token Balances
The Hacker News
Read on The Hacker News (opens in a new tab)Ref 00EEZUX7
Cite this
APA
Interestana AI Editorial. (2026, October 23). x402 SDK Flaw Risks AI Agents' Token Balances. Interestana. https://interestana.com/articles/critical-x402-sdk-flaw-could-let-malicious-apis-drain-ai-agents-token-balances-00eezux7
MLA
“x402 SDK Flaw Risks AI Agents' Token Balances.” Interestana, 23 Oct. 2026, interestana.com/articles/critical-x402-sdk-flaw-could-let-malicious-apis-drain-ai-agents-token-balances-00eezux7.
Chicago
Interestana AI Editorial. “x402 SDK Flaw Risks AI Agents' Token Balances.” Interestana, October 23, 2026. https://interestana.com/articles/critical-x402-sdk-flaw-could-let-malicious-apis-drain-ai-agents-token-balances-00eezux7.
BibTeX
@misc{interestana_00eezux7,
author = {{Interestana AI Editorial}},
title = {{x402 SDK Flaw Risks AI Agents' Token Balances}},
howpublished = {Interestana},
year = {2026},
month = oct,
url = {https://interestana.com/articles/critical-x402-sdk-flaw-could-let-malicious-apis-drain-ai-agents-token-balances-00eezux7},
note = {Summary of reporting by The Hacker News, https://thehackernews.com/2026/10/critical-x402-sdk-flaw-could-let.html}
}Credit the source
Original reporting: The Hacker News, “Critical x402 SDK Flaw Could Let Malicious APIs Drain AI Agents’ Token Balances”, https://thehackernews.com/2026/10/critical-x402-sdk-flaw-could-let.html(opens in a new tab)
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