Hardening NPM Repos

Modern software development relies heavily on open-source dependencies, and JavaScript projects—especially those using npm—are among the most dependency‑dense ecosystems in existence. With supply‑chain attacks, typo‑squatting, malicious maintainers, and vulnerable packages becoming increasingly common, it's essential to harden npm‑based repositories to protect both developers and end users.

This guide outlines practical, immediately actionable steps to secure your Node.js project.

Why Hardening Matters

An npm install may pull in thousands of transitive dependencies. Any one of them can introduce:

• Vulnerabilities (CVEs): That expose your application to security risks
• Malicious Scripts: That run automatically during installation
• Dependency Hijacking Attacks: Compromised packages can steal data or inject malware
• Unexpected Breaking Changes: Version updates can break your application unexpectedly

Hardening your repository reduces your attack surface and makes your builds deterministic, reproducible, and safer.

Run npm audit in Your CI Pipeline

Security checks should never rely on someone remembering to run them manually. Integrate npm audit directly in the CI pipeline.

Example snippet:

name: Security Audit
on: [push, pull_request]

jobs:
  audit:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-node@v4
        with:
          node-version: 24
      - run: npm ci
      - run: npm audit --audit-level=low

This prevents merging code that introduces known vulnerabilities.

Use npm ci for Reproducible Installs

npm ci installs dependencies exactly as specified in package-lock.json.

• No Drifting Versions: Dependencies install exactly as specified
• Faster Installations: Optimized for CI/CD environments
• Deterministic Builds: Ensures production builds match local builds

In CI/CD environments, always use:

npm ci

Never use npm install during automated builds.

Add no‑scripts to .npmrc

One of the most common attack vectors is malicious lifecycle scripts (postinstall, preinstall, etc.). A simple defense is disabling script execution by default.

In your .npmrc:

ignore-scripts=true

Or enforce the stronger setting:

fund=false
audit=true
ignore-scripts=true

When scripts are genuinely needed for development (e.g., building native modules), developers can run:

npm install --ignore-scripts=false

This prevents arbitrary code execution during automated installs or CI environments.

Pin All Dependencies

Never use ranges like:

• ^1.2.3: Allows minor and patch updates
• ~4.5.6: Allows patch updates only
• ***: Allows any version (extremely dangerous)

Ranges allow unintended upgrades, which can introduce malicious or broken versions.

Instead, pin exact versions in package.json:

"dependencies": {
  "express": "4.18.3"
}

Then commit your package-lock.json file to the repo.

Use Conventional Commits

Security and auditing are difficult when commit histories are messy. By enforcing the Conventional Commits specification, you ensure that every change to the codebase follows a structured format (e.g., fix:, feat:, chore:). This makes the project history machine-readable and transparent, allowing for automated changelog generation and easier identification of when a vulnerability was introduced or patched.

Add this to your package.json:

{
  "scripts": {
    "preinstall": "git config core.hooksPath .git-hooks",
  }
}

Add this to .git-hooks/commit-msg:

#!/bin/sh
# Get the commit message (the parameter we're given is just the path to the
# temporary file which holds the message).
commit_message=$(cat "$1")

if echo "$commit_message" | grep -Eq "^(build|chore|ci|docs|feat|fix|perf|refactor|revert|style|test)(\([a-z0-9 \-]+\))?!?: .+$"; then
  tput setaf 2
  echo "✔ Commit message meets Conventional Commit standards"
  tput sgr0
  exit 0
fi

tput setaf 1;
echo "❌ Commit message does not meet the Conventional Commit standard!"
tput sgr0;
echo "An example of a valid message is:"
echo "  feat(login): add the 'remember me' button"
echo "📝 More details at: https://www.conventionalcommits.org/en/v1.0.0/#summary"
exit 1

Release with Semantic Versioning

For a hardened repository, the release process must be deterministic and trustworthy. Semantic Versioning (SemVer) ensures that security patches (patch bumps) are clearly distinguished from breaking changes (major bumps). This allows consumers of your package—or your own internal services—to accept security updates automatically without fear of crashing production.

Automate this process to remove human error. Tools like standard-version or semantic-release can automatically determine the next version number based on your Conventional Commits.

Run a Licence Checker

Supply-chain security isn't just about malware; it is also about legal compliance. Bringing in a dependency with an incompatible license (like AGPL in a proprietary commercial application) can be a "legal vulnerability" that exposes your intellectual property or triggers lawsuits.

Since npm install brings in transitive dependencies you may never see, you must automate the auditing of these licenses. Use a tool like license-checker to fail the build if a forbidden license is detected.

Add this as a script in your package.json:

"scripts": {
  "audit:licenses": "license-checker --production --onlyAllow='MIT;ISC;Apache-2.0;BSD-3-Clause' --summary"
}

Further Reading

Some additional tips and suggestions are available at this link

Final Thoughts

Hardening an npm repository is not difficult - it just requires discipline. Implementing checks such as pinned dependencies, disabled scripts, reproducible installs, and automated auditing dramatically reduces supply‑chain risk.

By codifying these steps into CI pipelines and development workflows, your project becomes safer, more predictable, and far more resilient to modern threats.