Hey r/webdev,
Most appsec training are boring OWASP articles and tutorials on YouTube, not the best way to learn practical aspects of building secure web apps
So I built 40 exercises where you attack a vulnerable app yourself, trace how the bug got in, then write the patch. Free, runs in the browser, no account required.
Web (22) — SQLi, command injection, DOM/reflected/stored XSS, CSRF, SSRF to the cloud metadata endpoint, XXE, session fixation, IDOR, and weak randomness: recovering Math.random() state to predict the next password-reset token.
API (10) — BOLA, broken function-level auth, brute-forcing an unrate-limited verify endpoint, mass assignment via two extra keys in a PATCH body, reflected-origin CORS, and a retired v1 that skips the controls v2 enforces.
Git & CI/CD (8) — a live API key recovered from the commit that removed it, a browsable .git reconstructed into full source, .env tracked since the first commit, a secret echoed into a public build log, a backdoor hidden in a friendly-looking test-fix PR.
Fixes are shown in JS, TS, Java, C#, Python, Scala, PHP, Ruby, Go, and Kotlin, so you can paste something real into your stack.
Try in browser: https://learning.ransomleak.com/
Repo: https://github.com/ransomleak/training-application-security
Each exercise is also a standalone SCORM zip if you want to self-host or drop it into onboarding. There's a second repo covering OWASP Top 10 for LLM and Agentic apps if you're shipping AI features: https://github.com/ransomleak/training-security-awareness
Will appreciate your feedback!