A worm campaign attributed to TeamPCP compromised 169 npm packages and multiple PyPI packages, affecting an estimated 520 million cumulative downloads by injecting malicious code into projects including TanStack, OpenSearch, UiPath, and Mistral AI. The attack exploited three GitHub Actions weaknesses to move laterally across CI/CD pipelines without stolen credentials, then published poisoned packages bearing valid SLSA Build Level 3 provenance attestations, the same cryptographic trust signal organizations use to verify software supply chain integrity. The May 12, 2026 public release of the worm source code means copycat campaigns are now a near-term certainty, and any organization treating SLSA provenance as a sufficient integrity control is currently operating on a false assumption.