The Most Disregarded Question in the Recent NPM Supply Chain Attack That Developers Need Answers For

The recent NPM supply chain attacks affecting over 2 billion weekly downloads have prompted extensive security analysis across the industry. However, most reporting has focused on attack detection and the theoretical scale of the attack, while ignoring a fundamental question relevant to many organizations: “Is the version that we’re using in our supply chain affected?”

Or in other words: “If I use @crowdstrike/falcon-styles in version 4.1.2, am I compromised or not?”

The GitHub package advisories and the many scanners that popped up quickly thanks to vibe slotting do not seem to be able to answer this question properly.

This analysis gap represents a missed opportunity to understand real-world defensive effectiveness. Organizations implementing package locking for stable release processes may have been inherently protected, yet this protective factor has received limited attention in current security discussions.

During the worm propagation, the timing factor proved significant: Malicious packages remained available for approximately two hours before removal by npm’s security team. During this window, automated build systems and dependency management tools could download compromised versions if they were using the latest version of a package, but what about locked ones?

Attack Methodology and Package Management Implications

The September 2025 attack involved compromised maintainer accounts that published malicious versions of widely-used packages including chalk, debug, and related utilities. The attack execution included a specific command sequence:

npm version patch --force && npm publish --access public --token ${token}

This approach created new package versions containing malicious code rather than modifying existing releases. Attackers must increment version numbers to distribute malicious updates.

Organizations using package locking through package-lock.json or yarn.lock files would have avoided exposure to these attacks unless they updated their locked version while the malicious packages were still online!

The npm build mechanism operates through version pinning that references specific package releases predating malicious publications.

When attackers published compromised versions, locked dependencies continued referencing earlier, clean versions.

The malicious releases never entered environments with properly maintained lock files. This protection extends to transitive dependencies captured within lock file specifications.

The reason is NPM’s registry immutability principle. Once published for longer than 72 hours, package versions cannot be modified unless there is a bug in the enforcement on the npmjs side. So far the malware was not observed to try to unpublish recently published packages or having exploited any vulnerabilities to overcome policy enforcement.

For safety we recommend to set the following into the pnpm config:

# enforce package age > 72h
minimumReleaseAge: 259201

Organizations referencing specific versions through lock files maintain stable dependency trees unless deliberately updated through development processes that hopefully include review procedures.

Post-Compromise Detection Considerations

While package locking provides protection against the described attack vector, organizations should consider broader security scenarios. Successful compromise of development environments or CI/CD systems could enable attackers to modify dependency management processes or access sensitive information through other means.

Post-compromise activities often involve reconnaissance using legitimate security tools. The Shai Hutus worm employs utilities like TruffleHog to scan repositories for embedded secrets, API keys, or credential information. The effectiveness of such reconnaissance depends on organizational practices around secret management and repository hygiene.

Detection of these activities requires monitoring capabilities that can identify unusual repository scanning patterns, unexpected secret enumeration, or abnormal access to development resources. Traditional security controls focused on preventing initial compromise may not address these subsequent threat activities.

Comprehensive Supply Chain Security

The npm incident highlights the importance of multi-layered supply chain security approaches. Effective programs combine preventive measures like package locking and credential hygiene with detection capabilities that monitor development environments and dependency management processes.

Organizations benefit from understanding their complete software bill of materials, including direct and transitive dependencies across all environments. This visibility enables rapid impact assessment when new vulnerabilities emerge and supports informed decision-making about dependency updates.

The Nemesis platform addresses these requirements by providing continuous validation of security controls for supply chains and development environments.

Implementation Recommendations

Organizations should implement package locking as part of standard dependency management practices. This includes maintaining current lock files across all environments and establishing review processes for dependency updates. Version pinning should cover both direct dependencies and transitive packages captured in lock file specifications.

Beyond preventive measures, organizations should develop detection capabilities for post-compromise scenarios. This includes monitoring repository access patterns, unusual secret scanning activities, and unexpected changes to dependency management configurations.

Integration of dependency tracking supports proactive risk management. Organizations can assess potential exposure when new vulnerabilities are disclosed and make informed decisions about update priorities based on actual usage patterns.

Conclusion

The recent npm supply chain attacks demonstrate both the ongoing threats facing modern development practices and the protective value of well-implemented dependency management. Organizations with comprehensive package locking were likely protected against these specific attacks, though this defensive factor has received limited recognition in current security discourse.

Understanding which defensive measures provide actual protection during real-world incidents enables more informed security investment decisions. The npm attacks provide a useful case study for evaluating the effectiveness of different supply chain security approaches.

Persistent Security’s Nemesis platform provides supply chain visibility and threat detection capabilities that help organizations understand their security posture across the complete software development lifecycle.