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Web Security Basics

Protecting sites from XSS, CSRF and injection.

How it works

Web security protects applications and users from attacks. Key threats from the OWASP Top 10 include injection such as SQL injection, cross-site scripting where attacker scripts run in a victim's browser, cross-site request forgery that makes a logged-in browser send unwanted requests, broken authentication and access control, insecure deserialization, vulnerable dependencies and misconfiguration. Defenses include input validation, output encoding, parameterized queries, Content Security Policy, secure cookies, HTTPS with HSTS and least privilege.

Step-by-step walkthrough

  1. XSS injects a script into a page, so escape output.
  2. CSRF tricks a logged-in browser into sending a request.
  3. Use SameSite cookies and tokens.
  4. SQL injection puts commands in input, so use parameterized queries.
  5. Always validate input, use HTTPS and set security headers.

Where it is used

Every site that handles accounts or data needs these measures, and security headers, dependency scanning and penetration tests are part of normal engineering practice.

Common pitfall

Trusting client-side checks, building queries or HTML from raw input and leaving default credentials are classic mistakes. Security is not a feature to add at the end. Keep dependencies updated, never log secrets, apply defense in depth and review code for the OWASP categories.

Where it fits in the course

Web Security Basics is topic 41 of 51 in Web Development, rated Advanced. It follows CORS. The next topic is Web Performance.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Web Development quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Web Security Basics?
Protecting sites from XSS, CSRF and injection. It belongs to Web Development and is an advanced-level topic.
Where do people use Web Security Basics?
Every site that handles accounts or data needs these measures, and security headers, dependency scanning and penetration tests are part of normal engineering practice.
What is the most common mistake with Web Security Basics?
Trusting client-side checks, building queries or HTML from raw input and leaving default credentials are classic mistakes.
What should I learn before this topic?
Start with CORS, the topic just before it in Web Development.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Web Development quiz.
Is Web Security Basics hard to learn?
It is an Advanced topic. Expect to read the explanation more than once and to connect it with earlier topics. Working through a small example by hand helps most.
How long does it take to learn Web Security Basics?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Web Security Basics?
CORS, Web Performance, OAuth 2.0 are closely connected. The full list is in the related topics section of this page.
What should I study after Web Security Basics?
Continue with Web Performance, the next topic in Web Development.

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