Web Application Security: OWASP Top 10

It is for students and freshers who can build a basic web app in Python, JavaScript or Java and understand HTTP requests, cookies and basic SQL, but have not studied security. Code examples use Python with Flask and JavaScript with Node and Express, alongside raw HTTP requests and responses, so Java developers can follow the ideas even where the syntax differs. It suits developers doing their first code reviews, testers moving toward security testing, and anyone who wants to stop shipping the bugs that keep appearing in security reports.

If you mainly review Python code, including code written by AI assistants, Secure Coding & Reviewing AI-Written Code focuses on that. For a broader view of security that includes networks and incident response, Cybersecurity Interview Mastery covers that ground. This course stays with web applications and the code behind them.

Each lesson is a short set of reading cards built around one flaw or one defence, usually with a few lines of vulnerable code next to the fixed version, and diagrams where a request flow is easier to see than to describe. You can read the cards or listen to the narration. A multiple-choice quiz follows every lesson, with an explanation after each answer, and you can ask the AI guide about any card or question. Questions ask which input breaks a snippet, whether a fix actually works, which header or cookie attribute a situation needs, or which OWASP category a bug belongs to. Lessons open in order on a course map.

The course is defensive. Attack inputs appear only to show why code is vulnerable; it does not teach step-by-step use of offensive tools and never asks you to test systems you do not own. A full topic covers secure code review, dynamic testing, scope and safe testing, and responsible disclosure.

The last topic compares ideas that are easy to mix up, such as encryption versus signing, CSRF versus XSS, session cookies versus JWTs and a bug bounty versus a penetration test, then applies them to real tasks: hardening a login endpoint, securing an upload flow, reviewing a pull request and responding to a CVE alert.

Udemy and Coursera teach web security mostly through recorded video lectures, and PortSwigger Web Security Academy offers interactive labs where you exploit deliberately vulnerable applications in a safe environment. Labs are the right choice if you want hands-on exploitation practice. This course is built for a different job: reading code, recognising the flaw and knowing the fix, which is what developers and reviewers do day to day. Short lessons and a quiz after each one check that you can spot an IDOR or an unsafe innerHTML in a snippet, not just define it.

Learn to see trust boundaries first. Many vulnerability classes come back to data from an untrusted source reaching something that trusts it: a SQL interpreter, a browser, a shell, an internal URL or a deserializer. Once you ask where each input comes from and what will interpret it, many bugs become visible. Then learn the standard fix for each class and why it works, rather than memorising lists of attack payloads.

These mistakes come up again and again in the course, and they are worth checking for in your own code:

• Relying on client-side checks for access control or validation
• Building SQL, shell or template strings from user input
• Hashing passwords with a fast plain hash instead of bcrypt or Argon2
• Treating encoding as if it were encryption
• Leaving debug mode, default credentials or verbose error pages on in production
• Trusting a JWT without checking its signature and algorithm
• Committing secrets to source code or CI configuration

Use each lesson's quiz as active recall, revisit the lessons where you got questions wrong, and try the habits on a project you own, for example by running a dependency scan or reviewing your own login and upload code.