CORS gets "fixed" with *.
Access-Control-Allow-Origin: * can silence the error while teaching you nothing about which origins your server now trusts.
A 60-minute browser security lab for modern web devs
Web security judgment is your edge in the AI era.
Start the 60-minute security lab
Launch price €19 Regular €37
Learn the browser rules every web app depends on: Same-Origin Policy, CORS, CSP, violation reporting, and Subresource Integrity, so you can see what the browser protects, what your server allows, and what generated or copied code can quietly assume.
Trusted by 500+ developers including engineers from:
The hidden problem
The dangerous code is often the code that works.
Browser security failures rarely introduce themselves as security failures. They show up as harmless-looking headers, console errors, external scripts, and AI-generated glue code.
CSP headers get copied.
But copied policies rarely teach what still executes, what gets blocked, and what damage remains possible.
Generated code gets trusted.
AI can produce code that passes the happy path while hiding insecure assumptions about origins, scripts, and resources.
Origins get misunderstood.
But if you cannot explain what the browser isolates, you cannot tell when generated code crosses a trust boundary.
Third-party scripts get waved through.
One analytics tag, widget, or CDN asset can become your problem if you do not know how the browser limits what it can do.
Local demos look safe.
Then production adds domains, headers, redirects, embeds, and generated code paths your browser security model was never ready to inspect.
Unknown unknowns
If you cannot model the boundary, you cannot review the code.
- You fixed a cross-origin issue without knowing which party became trusted.
- You use third-party scripts without knowing how to limit the blast radius.
- You know Same-Origin Policy exists, but cannot reason from it under pressure.
- You review AI-generated frontend code by behavior, not by browser security model.
Developer reactions
That “we got it wrong” moment.
The point is not trivia. It is finally seeing what the browser is enforcing.
What you will learn
Five browser-layer rules that change how you review web code.
The starter kit is intentionally narrow. In one focused path, you build the mental model behind the browser decisions that break, protect, or quietly expose modern web apps.
Part 1
Same-Origin Policy
The browser's default rule for deciding which sites can read from each other.
know when code crosses a trust boundary
Part 2
Cross-Origin Resource Sharing
The server-side permission system that decides which other origins may access your responses.
stop reaching for Access-Control-Allow-Origin: *
Part 3
Content Security Policy
A browser policy that limits which scripts and resources are allowed to run.
stop trusting copied CSP headers
Part 4
Violation Reporting
A way to see when browser security policies fail or get triggered in real apps.
turn silent policy failures into signals
Part 5
Subresource Integrity
A browser check that verifies third-party files have not changed unexpectedly.
verify the code you did not write
Outcome Browser security assumptions checked
You end with a sharper model for how browsers execute code, enforce origins, apply policies, surface violations, and trust third-party resources.
Ready to build this model in 60 minutes?
Start the 60-minute security lab
€19 launch price. 14-day refund. Instant access.
Hands-on labs
Understand the concepts first.
Move through short focused lessons and visual explanations before you touch the code, so SOP, CORS, CSP, reporting, and SRI stop feeling like disconnected acronyms.
Run code yourself
Then see the browser enforce the rules locally.
Run browser and server examples, inspect failures, adjust headers, and watch the mental model become visible in behavior you can explain.
security-labs % npm run policies
CSP violation captured
report-uri received: blocked inline script
SRI check passed for trusted asset
Learner proof
Developers remember explanations that change how they debug.
The goal is not to collect tips. It is to understand the browser well enough to reason when real code starts failing.
Why this matters now
Browser security understanding becomes more valuable as more code is produced with AI.
Generated code can pass the happy path while hiding broken assumptions about origins, scripts, and resources. The developer who can spot those assumptions becomes harder to replace.
Who it is for
Built for developers who ship web apps and know security is a blind spot.
Frontend developers moving deeper into app security Full-stack JavaScript developers shipping real apps AI-assisted developers reviewing generated code Ambitious juniors and mid-level developers building senior judgment
Credibility
Taught by a developer who knows where developers actually get stuck.
Bartosz Pietrucha
Software engineer, security educator, conference speaker, and Snyk Ambassador.
- Taught thousands of developers worldwide
- Worked on enterprise software across finance, security, and commerce
- Runs Web Security Dev Academy
Built from real developer confusion.
The labs focus on the places where working developers usually paper over the browser model: origins, credentials, script execution, reporting, and third-party assets.
Small enough to finish. Technical enough to matter.
One 60-minute foundation lab, source code you can run locally, and a checklist you can keep nearby when reviewing generated or teammate-written code.
Included extras
The focused lab, plus useful security context around it.
The main product is the browser security lab. These extras help you connect that model to authentication, OWASP risks, community support, and review checklists.
JWT attack walkthrough
See how JSON Web Tokens can fail when implementation assumptions are wrong.
TOTP / 2FA explainer
Understand the moving parts behind time-based one-time passwords.
OWASP Top 10 deep dive
A broader security reference for common web application risks.
Security-oriented developer community
Ask questions and learn alongside developers who care about web security.
Named PDF certificate
A simple completion certificate for your records.
Modern web app security checklist
Seven practical steps for reviewing security assumptions in modern web apps.
The offer
Browser Security Starter Kit
For €19, get the focused browser security lab, local source code, the review checklist, supporting security extras, community access, and a 14-day refund window.
Learning path
This is the browser foundation. The full academy goes deeper.
Web Security Dev Academy expands into authentication, backend security, testing, architecture, and production hardening. This starter kit gives you the browser model that makes those deeper topics easier to reason about.
FAQ
Questions developers usually ask before starting.
Is this for beginners?
It is beginner-friendly if you already build web apps. You do not need security experience, but you should be comfortable with basic frontend and server concepts.
Is this only frontend security?
No. The browser is the starting point, but the labs connect browser behavior to server decisions like origins, headers, and resource delivery.
Do I need to become a security specialist?
No. The goal is practical judgment: understanding the browser rules your app depends on so you can spot insecure assumptions earlier.
Do I get source code?
Yes. The starter kit is built around hands-on labs and source code you can run locally.
Is there a refund?
Yes. Try the starter kit for 14 days. If it is not useful, email me and I'll refund you.
Is this part of Web Security Dev Academy?
It is the foundation layer. Web Security Dev Academy goes deeper into authentication, backend security, testing, architecture, and production hardening.
Stop reviewing generated web code with a blind spot.
In 60 minutes, build the browser security model behind origins, policies, violations, and third-party resources.
Start the 60-minute security lab