
How a Misconfigured CI Workflow Became an npm Supply-Chain Compromise | Blog | Endor Labs
Endor Labs breaks down the May 11, 2026 compromise of 42 @tanstack/* npm packages (84 malicious versions) that carried valid SLSA provenance. The attacker chained a pull_request_target "Pwn Request", GitHub Actions cache poisoning across the fork/base boundary, and OIDC token extraction from Runner.Worker memory, then published directly to npm without stealing any credential. It explains why 2FA, trusted publishing, provenance and branch protection all failed, and lists mitigations: split pull_request_target workflows, treat the cache as untrusted, scope id-token: write to a publish job, pin actions to SHAs, require environment approval, use egress allowlists.
Supply Chain, DevSecOps· Published and added 12 Oct 2026

























