Dangerous by default: Insecure GitHub Actions found in MITRE, Splunk, and other open source repositories

The Sysdig Threat Research Team discovered that many open-source GitHub Actions workflows using the pull_request_target trigger are misconfigured, enabling attackers to check out untrusted code from forks, run malicious install steps (e.g., via pip/setup.py), exfiltrate secrets (including high-privilege GITHUB_TOKENs) and take over repositories; the report details confirmed incidents against Spotipy (CVE-2025-47928), MITRE CAR, and Splunk, and provides mitigation guidance such as splitting workflows, restricting GITHUB_TOKEN permissions, label gating, and using runtime detection with Falco Actions.