Postmortem: TanStack npm supply-chain compromise via GitHub Actions exploitation
By
Tanner Linsley
Hot, fresh, and worth queueing round the block for.
Summary
On May 11, 2026, an attacker exploited a chain of vulnerabilities — including the pull_request_target "Pwn Request" pattern, GitHub Actions cache poisoning across the fork↔base trust boundary, and runtime memory extraction of an OIDC token — to publish 84 malicious versions across 42 @tanstack/* npm packages. No npm tokens were stolen and the npm publish workflow itself was not compromised. The malicious versions were detected within 20 minutes by an external researcher. This postmortem details the attack timeline, root cause analysis, and remediation steps taken by the TanStack team.
Key quotes
· 3 pulledOn 2026-05-11 between 19:20 and 19:26 UTC, an attacker published 84 malicious versions across 42 @tanstack/* npm packages by combining: the pull_request_target 'Pwn Request' pattern, GitHub Actions cache poisoning across the fork↔base trust boundary, and runtime memory extraction of an OIDC token from the GitHub Actions runner process.
No npm tokens were stolen and the npm publish workflow itself was not compromised.
The malicious versions were detected publicly within 20 minutes by an external researcher ashishkurmi working for step
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