OWASP Top 10 for Startups: A No-Nonsense Implementation Guide

The OWASP Top 10 is the industry standard for web security risks, written in a way that makes startup founders' eyes glaze over. We translated it into concrete steps for TypeScript/Node.js applications.

Broken Access Control: users accessing data they should not. Implement RBAC from day one with middleware checking permissions before every route. Never rely on the frontend to hide unauthorized actions. Four to eight hours.

Cryptographic Failures: HTTPS everywhere, bcrypt for passwords (cost 12), encrypt PII database fields. Two to four hours.

Injection: parameterized queries exclusively, validate all input with Zod at API boundaries, never interpolate user input into SQL or templates. One to two hours.

Insecure Design: for every feature, ask "what if a malicious user does this a thousand times?" Spend thirty minutes threat modeling each feature during design.

Security Misconfiguration: security headers middleware (X-Content-Type-Options, X-Frame-Options, HSTS, CSP, Referrer-Policy), disable directory listing, remove server version headers. Two to three hours.

Vulnerable Components: automated dependency scanning in CI, pinned versions, weekly update reviews. Two to three hours setup.

Authentication Failures: use Clerk or Supabase Auth rather than building custom. Enforce twelve-character passwords, account lockout after five failed attempts, secure cookies. Two hours with auth service.

Data Integrity Failures: validate all external data including webhook signatures, API responses against schemas, and file upload types. Three to four hours.

Logging Failures: log all auth events and authorization failures. Centralize with Axiom or Datadog. Alert on anomalies: ten-plus failed logins from one IP, admin actions outside hours. Three to four hours.

Server-Side Request Forgery: validate and allowlist all URLs the server fetches. Never let user input determine request destinations without validation. One to two hours.

Total: three to five days for greenfield, add one to two days for existing code audits. A tiny investment relative to a breach. We include it in every estimate as non-negotiable.