The Security track.

AppSec for working engineers — injection, auth, crypto, supply chain and secrets. Built as a curriculum — 8 chapters, recommended spine if you're new, side-quests when you're ready.

You'll cover: Injection, XSS, Auth — then go deeper.

Start here: SQL Injection: How a Login Form Leaks the Whole Database → Cross-Site Scripting (XSS): Stored, Reflected, DOM → Content Security Policy Blocked Inline Script →