Suspicious Obfuscation Marker in JavaScript Bundle from Compromised npm Package

ATT&CK techniques

Initial Access → Execution

Recon
Resource Dev
Initial Access
- T1195.002Compromise Software Supply Chain
Execution
- T1059.007JavaScript
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the specific hex-arithmetic obfuscation marker string embedded by the September 2025 debug and chalk npm supply chain attack in trojanized frontend bundles which was used to conceal the wallet-hijacking crypto-clipper payload. Presence of this marker indicates a compromised package version shipped into the build and warrants immediate dependency review.

Reporting behind it

Related detections9 linkedT1059.007 — drag to rearrange

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Malicious Shai-Hulud npm Worm Marker via SHA1HULUD Process Name (via process_creation)

Malicious Node.js Execution of Hidden .claude Setup Script

Suspicious npm Postinstall Node Execution From Fixtures Path (BeaverTail OtterCookie)

Suspicious NPM Install Hook Executing Setup Script via Node

Malicious Bun Runtime Payload Dropped by Shai Hulud npm Supply Chain Attack

Malicious Shai-Hulud Bun Payload Execution via npm Preinstall Script (via process_creation)

Malicious Shai-Hulud npm Payload Execution via bun_environment Script (via process_creation)

Suspicious Obfuscation Marker in JavaScript Bundle from Compromised npm Package

Pivot detection · T1059.007 · 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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