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Course 1 - BurpSuite Bug Bounty Web Hacking from Scratch | Episode 10: XSS: Overview, Security Level Testing, and Real-World Attacks
In this lesson, you’ll learn about:
You can listen and download our episodes for free on more than 10 different platforms:
https://linktr.ee/cybercode_academy
- Definition of Cross-Site Scripting (XSS):
A client-side web vulnerability where an application executes user-supplied JavaScript instead of treating it as text. It typically occurs in user input areas such as search fields, comment boxes, or feedback forms. - Main Types of XSS:
- Reflected XSS (Non-persistent):
- The malicious input is not stored in the database.
- It only affects users who execute the injected script (e.g., by clicking a crafted link).
- Commonly found in search or URL parameters.
- Stored XSS (Persistent):
- The injected payload is saved in the application database (e.g., in comments).
- The script runs automatically for every visitor who loads the infected page.
- This type has a higher impact and broader reach.
- DOM-based XSS:
- The vulnerability exists in the Document Object Model (DOM) layer.
- The HTML response may appear unchanged, but JavaScript execution happens client-side.
- Reflected XSS (Non-persistent):
- Potential Consequences:
- Theft of cookies and session tokens.
- Hijacking user accounts or sessions.
- Launching Cross-Site Request Forgery (CSRF) attacks.
- Delivering malicious redirects or keyloggers.
- Practical Demonstrations:
- Reflected XSS (OWASP Mutillidae Example):
- Using Burp Suite to intercept and inject a simple payload:
- If the response returns the payload unmodified, the application is vulnerable.
- DVWA Demonstrations Across Security Levels:
- Low Level: The script runs immediately without filters.
- Medium Level: Filtering is attempted (e.g., removing the word “script”). Bypassed using mixed-case payloads like:
- High Level: Stronger filtering, but DOM-based XSS succeeds using:
- Reflected XSS (OWASP Mutillidae Example):
- Real-World Exploitation Example:
- Attackers send phishing emails containing legitimate-looking links that include malicious JavaScript in the query string.
- When clicked, the script executes on the target site, allowing theft of credentials or session data.
- This is often referred to as first-order XSS, primarily exploiting GET requests.
- Prevention Techniques:
- Validate and sanitize all user input (both client and server-side).
- Implement output encoding for HTML, JavaScript, and URL contexts.
- Use modern Content Security Policy (CSP) headers.
- Avoid using innerHTML for dynamic content updates.
- Educate users to verify links before clicking, especially in unsolicited emails.
You can listen and download our episodes for free on more than 10 different platforms:
https://linktr.ee/cybercode_academy
View all episodes
By CyberCode AcademyIn this lesson, you’ll learn about:
You can listen and download our episodes for free on more than 10 different platforms:
https://linktr.ee/cybercode_academy
- Definition of Cross-Site Scripting (XSS):
A client-side web vulnerability where an application executes user-supplied JavaScript instead of treating it as text. It typically occurs in user input areas such as search fields, comment boxes, or feedback forms. - Main Types of XSS:
- Reflected XSS (Non-persistent):
- The malicious input is not stored in the database.
- It only affects users who execute the injected script (e.g., by clicking a crafted link).
- Commonly found in search or URL parameters.
- Stored XSS (Persistent):
- The injected payload is saved in the application database (e.g., in comments).
- The script runs automatically for every visitor who loads the infected page.
- This type has a higher impact and broader reach.
- DOM-based XSS:
- The vulnerability exists in the Document Object Model (DOM) layer.
- The HTML response may appear unchanged, but JavaScript execution happens client-side.
- Reflected XSS (Non-persistent):
- Potential Consequences:
- Theft of cookies and session tokens.
- Hijacking user accounts or sessions.
- Launching Cross-Site Request Forgery (CSRF) attacks.
- Delivering malicious redirects or keyloggers.
- Practical Demonstrations:
- Reflected XSS (OWASP Mutillidae Example):
- Using Burp Suite to intercept and inject a simple payload:
- If the response returns the payload unmodified, the application is vulnerable.
- DVWA Demonstrations Across Security Levels:
- Low Level: The script runs immediately without filters.
- Medium Level: Filtering is attempted (e.g., removing the word “script”). Bypassed using mixed-case payloads like:
- High Level: Stronger filtering, but DOM-based XSS succeeds using:
- Reflected XSS (OWASP Mutillidae Example):
- Real-World Exploitation Example:
- Attackers send phishing emails containing legitimate-looking links that include malicious JavaScript in the query string.
- When clicked, the script executes on the target site, allowing theft of credentials or session data.
- This is often referred to as first-order XSS, primarily exploiting GET requests.
- Prevention Techniques:
- Validate and sanitize all user input (both client and server-side).
- Implement output encoding for HTML, JavaScript, and URL contexts.
- Use modern Content Security Policy (CSP) headers.
- Avoid using innerHTML for dynamic content updates.
- Educate users to verify links before clicking, especially in unsolicited emails.
You can listen and download our episodes for free on more than 10 different platforms:
https://linktr.ee/cybercode_academy