One Supply Chain Attack to Rule Them All - Poisoning GitHub's Runner Images

Preface Let’s think for a moment what a nightmare supply chain attack could be. An attack that would be so impactful that it could be chained to target almost every company in the world. For an attacker to carry out such an attack they would need to insert themselves into a component fundamental to building the largest open-source software projects on the Internet. What would an attacker need to target in order to carry out this attack? Cloud infrastructure would certainly qualify. What about build agents? Those would certainly be impactful, and SolarWinds put that attack on the map. If an attacker wanted more, the attacker would instead need to target SaaS companies providing hosted build services. Services like GitLab CI, TravisCI, CircleCI, BuildKite, and GitHub Actions fall within this category.