Cross-Site Scripting (XSS) Defense Fundamentals

Web applications face constant security risks, with Cross-Site Scripting (XSS) remaining one of the most critical vulnerabilities on the internet. Understanding how malicious scripts are injected into web pages is essential for anyone involved in building or securing web solutions. This written course provides a thorough grounding in XSS fundamentals, guiding you from basic browser behavior to modern defense strategies. You will learn how attackers exploit web inputs, how sessions are compromised, and how to write resilient code that prevents unauthorized script execution. What you'll learn: - Understand foundational web security concepts, browser context, and session management. - Distinguish between stored, reflected, and DOM-based XSS attack patterns. - Analyze how attackers steal cookies and perform session hijacking. - Apply context-aware output encoding and sanitization techniques. - Configure modern defenses such as Content Security Policy (CSP) headers and HttpOnly cookies. - Explore modern framework security mechanisms that automatically mitigate injection risks. Starting with essential definitions and core HTTP concepts, the course moves step-by-step into vulnerability identification and practical defensive patterns. It is tailored for beginner developers, software engineering students, and web enthusiasts with no prior security background. Begin reading to master the essentials of XSS defense and build safer web applications.