Security best practices in express.js

Why is security important in express.js?

Express.js is one of the most popular web frameworks for Node.js, which also makes it a common target for attackers. By following a set of best practices, you can significantly reduce your app’s exposure to common web threats like cross-site scripting (XSS), injection, or cross-site request forgery (CSRF).

Common vulnerabilities and how to prevent them

1. Cross-site Scripting (XSS)

Problem: Injected scripts executed in the browser.

Solution:

• Sanitize user inputs using libraries like DOMPurify (for frontend) or xss-clean.
• Use templating engines that auto-escape (like Pug or EJS).
• Set HTTP headers using helmet.

const helmet = require("helmet");
app.use(helmet());

2. NoSQL/SQL Injection

Problem: Malicious input modifies database queries.

Solution:

• Use parameterized queries or ORM methods (e.g., Prisma, Sequelize).
• Never interpolate user input directly into queries.

3. Cross-site Request Forgery (CSRF)

Problem: Unauthorized commands submitted on behalf of an authenticated user.

Solution:

• Use csurf middleware to validate tokens on state-changing requests.

const csrf = require("csurf");
app.use(csrf());

4. Insecure HTTP headers

Problem: Default headers can expose your app.

Solution:

• Use helmet to configure secure headers like:
• Content-Security-Policy
• Strict-Transport-Security
• X-Frame-Options

5. Sensitive data exposure

Problem: Leaking of API keys, tokens, or passwords.

Solution:

• Use environment variables (.env files) for secrets.
• Never commit secrets to Git.
• Use .gitignore for sensitive files.

6. Rate limiting and brute force protection

Problem: Attackers can attempt password guessing or abuse endpoints.

Solution:

• Use express-rate-limit to limit repeated requests.

const rateLimit = require("express-rate-limit");

app.use(rateLimit({
  windowMs: 15 * 60 * 1000,
  max: 100
}));

Additional best practices

Best practices summary

• Use helmet for secure headers.
• Validate and sanitize all input.
• Store secrets securely.
• Use CSRF and rate limiting middleware.
• Keep dependencies up to date with tools like npm audit or snyk.

Conclusion

Security in Express.js doesn’t have to be overwhelming. By applying these best practices—headers, input validation, CSRF protection, and secure storage—you significantly reduce your app’s attack surface. Securing your Express app is a continuous process, but these steps give you a strong foundation.