Suspicious Double Base64 Encoding to Bypass GitHub Actions Secret Masking

ATT&CK techniques

Cred Access → C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
- T1552.001Credentials In Files
Discovery
Lateral Movement
Collection
C2
- T1132.001Standard Encoding
Exfiltration
Impact

What it detects

This rule detects the double Base64 encoding one-liner used to exfiltrate GitHub Actions secrets by circumventing the platform secret masking that only redacts the plaintext value. Chaining two base64 encodings on a secret is a deliberate evasion technique observed in GitHub PAT to cloud control plane attacks and rarely appears in legitimate build steps.

Reporting behind it

Related detections9 linkedT1552.001 — drag to rearrange

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Suspicious Double Base64 Encoding to Bypass GitHub Actions Secret Masking

Pivot detection · T1552.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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