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

This Sysdig Threat Research Team report demonstrates how insecure GitHub Actions workflows—particularly those using the pull_request_target trigger and checking out untrusted fork code—can be trivially exploited to run attacker-controlled code (via pip/install hooks or requirements) to exfiltrate secrets and high-privilege GITHUB_TOKENs; the team successfully exploited and reported issues in multiple well-known repositories (Spotipy — CVE-2025-47928, MITRE CAR, and Splunk) and provides mitigation guidance such as splitting workflows, restricting token permissions, and using runtime detection (Falco Actions).