Valid certificates, stolen accounts: how attackers broke npm's last trust signal

On May 19, 633 malicious npm package versions passed Sigstore provenance verification. They were cleared by the system because the attacker had generated valid signing certificates from a compromised maintainer account.Sigstore worked exactly as designed: it verified the package was built in a CI environment, confirmed a valid certificate was issued, and recorded everything in the transparency log. What it cannot do…