Security Best Practices for Modern Web Applications

Security isn't a feature you bolt on at the end — it's a property of every layer of your stack. These practices form the baseline for any production web application in 2024.

Authentication and Identity

Adopt OAuth 2.1 / OpenID Connect for federated identity, and require MFA for any account that holds privileged data. Store password hashes with Argon2id; never roll your own crypto.

Defense in Depth

No single control should be the only thing standing between an attacker and your data. Combine strict CSP, HSTS, subresource integrity, and a properly scoped CORS policy at the edge.

Input Validation and Output Encoding

Validate at every trust boundary, encode at every output. Use parameterized queries everywhere — SQL injection is still in the OWASP Top 10 because we keep concatenating strings.

Secrets Management

Never commit credentials. Use a vault (AWS Secrets Manager, HashiCorp Vault, Doppler) and rotate keys regularly. Audit access continuously.

Dependency Hygiene

Most compromises come from a vulnerable transitive dependency. Run automated SCA tools, pin versions, and review the supply chain before pulling in new packages.

Logging Without Leaking

Log security-relevant events — failed logins, privilege changes, large data exports — but redact PII and tokens aggressively before anything hits a log aggregator.

Plan for the Breach

Assume compromise. Have an incident-response runbook, practice it quarterly, and know exactly how you'll communicate with customers if the worst happens.