A critical security incident has been uncovered involving the popular GitHub Action tj-actions/changed-files, which is used in over 23,000 repositories.
The attack involves a malicious modification of the Action’s code, leading to the exposure of CI/CD secrets in GitHub Actions build logs.
This vulnerability was detected by StepSecurity’s Harden-Runner, a tool designed to secure CI/CD workflows by monitoring network activities and controlling access on GitHub-hosted and self-hosted runners.
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The compromised Action executes a malicious Python script that dumps sensitive data from the GitHub Actions runner’s memory.
The exploit specifically targets Linux environments, where it attempts to extract secrets by reading the memory of the Runner Worker process.
The malicious code was introduced through a retroactive update of multiple version tags, all pointing to the same malicious commit hash.
This sophisticated attack strategy allowed the attackers to compromise most versions of the Action without immediately raising suspicion.
Incident Timeline
The incident began on March 14, 2025, and was quickly identified by StepSecurity’s anomaly detection capabilities.
By March 15, GitHub had removed the compromised Action, preventing further use in workflows.
However, the repository was later restored with all versions updated to exclude the malicious code.
To mitigate the impact, StepSecurity released a secure drop-in replacement for the compromised Action, recommending that users replace all instances of tj-actions/changed-files with step-security/changed-files.
Response
The attack highlights the risks associated with supply chain vulnerabilities in open-source software.
While there is no evidence that leaked secrets were exfiltrated to remote networks, public repositories are particularly vulnerable as their build logs are accessible to anyone.
Users are advised to review recent workflow logs for signs of leaked secrets and rotate these secrets immediately if found.
An official CVE (CVE-2025-30066) has been published to track this incident, emphasizing the need for proactive security measures in CI/CD pipelines.
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