Thanks again for your timely detection and reporting!
We strongly advise replacing all instances of tj-actions/changed-files in your workflows with our secure alternative: https://github.com/step-security/changed-files
The security industry tolerates self-promotion only to the extent that the threat research benefits everyone.
StepSecurity Harden-Runner detected this security incident by continuously monitoring outbound network calls from GitHub Actions workflows and generating a baseline of expected behaviors. When the compromised tj-actions/changed-files Action was executed, Harden-Runner flagged it due to an unexpected endpoint appearing in the network traffic—an anomaly that deviated from the established baseline. You can checkout the project here: https://github.com/step-security/harden-runner