Browser Security Best Practices

What this best practices guide is

A practical guide to browser security for web developers. It explains how cross-site scripting happens in modern frameworks and how Trusted Types and a strict Content Security Policy contain it, how to configure CORS without opening your API, which cookie attributes and prefixes to use, how to stop CSRF and clickjacking, which security headers matter, and how to load third-party scripts and talk between windows safely.

It has 7 chapters and 22 practices, each with why it matters, what to do and what to avoid. For web developers who ship pages to browsers.

Chapter by chapter

1. Cross-site scripting and Trusted Types (4 practices)

How XSS gets into apps built with modern frameworks, the code patterns that prevent it, and how Trusted Types lets the browser enforce those patterns for you.

2. Content Security Policy (3 practices)

A strict Content Security Policy tells the browser which scripts may run, so an injected one does not. These practices get you to a strict policy without breaking the site.

3. CORS done right (3 practices)

CORS does not protect your API; it relaxes the same-origin policy for origins you name. These practices keep that relaxation narrow.

4. Cookies (3 practices)

Cookie attributes decide which requests carry your session and which code can read it. Small settings here close entire classes of attack.

5. Cross-site request forgery (3 practices)

CSRF tricks a signed-in user's browser into sending a request they did not mean to. These are the defenses OWASP recommends, in the order to reach for them.

6. Framing, HSTS and security headers (3 practices)

A handful of response headers switch on protections the browser already has: no framing, HTTPS only, no content sniffing, fewer referrer leaks and isolated windows.

7. Third-party scripts and cross-window messaging (3 practices)

Every script you include runs with your page's full power, and every window you talk to could be someone else's. Load less, pin what you load, and check who is talking.

How it works on Sefism

The guide reads like a short course: a syllabus, then one chapter per page in a focused reader, with a quiz at the end of each chapter for members. The opening chapters are open to everyone. Adding it to your account uses credits, opens every chapter and keeps your progress.

Every claim is checked against the sources listed on the page (8 cited).