Suspicious npm Postinstall node Execution of setup.cjs with Warnings Suppressed

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1059.007JavaScript
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects node executing a setup.cjs script with the --no-warnings flag, the postinstall behavior used in the Mastra npm supply chain compromise attributed to Sapphire Sleet. A postinstall script suppressing warnings while running an installer stage is characteristic of malicious package code fetching a second stage payload.

Reporting behind it

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Suspicious npm Postinstall node Execution of setup.cjs with Warnings Suppressed

Pivot detection · T1059.007 · 9 related

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