After this lesson, you will be able to: Understand why security is part of every developer's job, what the most common ways web apps get compromised are, and how this subtrack takes you from zero to shipping secure code by default.
Security is not a separate team's problem you hand off at the end. The person who writes the code decides whether it is safe. This subtrack teaches the defenses every developer putting something on the internet is responsible for: keeping secrets out of code, rate limiting and bot protection, security headers, secure authentication, dependency safety, and HTTPS. None of this is advanced. It is table stakes.
This is a free introductory lesson. No purchase required.
Most breaches do not come from sophisticated nation-state hackers. They come from ordinary mistakes a developer made: an API key committed to a public repo, a login endpoint with no rate limit, a missing security header, an outdated dependency with a known vulnerability. Every one of those is a developer decision. If you build things that go on the internet, you are a security engineer whether you call yourself one or not.
The common paths: leaked credentials (a secret in Git history, a hardcoded key); brute force and credential stuffing against login forms with no rate limiting; cross-site scripting and clickjacking that security headers would have blocked; weak or missing authentication controls; a vulnerable npm package pulled in three dependencies deep; and traffic intercepted because HTTPS was not enforced. This subtrack has a lesson for each of these.
Store secrets correctly and clean them out of Git history if they leak. Add rate limiting to any endpoint. Stop bots and scrapers with layered defenses. Set a complete set of HTTP security headers in Next.js. Hash passwords, manage sessions, and implement MFA the right way. Audit your dependencies and respond to a supply-chain alert. Understand TLS, get a certificate, and lock down DNS. Then you will harden a real deployed app as a capstone.