JavaScript Security - Practice Questions 2026

Master JavaScript Security: XSS, CSRF, and CSP Practice Exams

Welcome to the definitive resource for mastering web security vulnerabilities and defenses. If you are looking to solidify your understanding of Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), and Content Security Policy (CSP), these practice exams provide the most comprehensive environment to test your skills and ensure your applications remain impenetrable.

Why Serious Learners Choose These Practice Exams

In the rapidly evolving landscape of web development, theoretical knowledge of security is no longer enough. Serious learners choose this course because it bridges the gap between reading a specification and applying that knowledge under pressure. These exams are designed to mimic real-world security audits and certification environments, providing deep dives into how attackers think and how defenders build resilient systems. By engaging with high-quality, original questions, you transition from a developer who "knows about" security to a professional who can implement it.

Course Structure

This course is meticulously organized into six distinct levels to ensure a logical progression of difficulty and conceptual depth:

• Basics / Foundations: This section focuses on the fundamental principles of the Same-Origin Policy (SOP), the document object model (DOM), and the basic execution flow of JavaScript. Understanding these "rules of the road" is essential before diving into specific vulnerabilities.

• Core Concepts: Here, we break down the primary mechanics of XSS and CSRF. You will learn to identify the differences between Reflected, Stored, and DOM-based XSS, as well as the fundamental requirements that make a CSRF attack possible.

• Intermediate Concepts: This level introduces defensive mechanisms. We explore how to properly implement Content Security Policy (CSP) directives, secure cookie attributes (HttpOnly, Secure, SameSite), and the nuances of input validation versus output encoding.

• Advanced Concepts: Challenge yourself with complex bypass techniques. This section covers CSP bypasses using whitelisted CDNs, polyglot payloads, and sophisticated CSRF scenarios involving multi-step actions or JSON-based requests.

• Real-world Scenarios: Move beyond isolated code snippets. These questions present architectural challenges and "broken" implementations based on actual historical vulnerabilities found in modern web frameworks and APIs.

• Mixed Revision / Final Test: The ultimate benchmark. This comprehensive exam pulls from all previous sections, forcing you to switch contexts rapidly and prove your readiness for professional security assessments.

Sample Practice Questions

QUESTION 1

A developer wants to prevent a Cross-Site Request Forgery (CSRF) attack on a sensitive POST action. Which of the following approaches is considered the most robust defense when used correctly?

• OPTION 1: Checking the Referer header to ensure the request originated from the same domain.

• OPTION 2: Implementing a unique, cryptographically strong Synchronizer Token (anti-CSRF token) mapped to the user session.

• OPTION 3: Using the HTTP GET method instead of POST for all sensitive state-changing operations.

• OPTION 4: Relying solely on the HttpOnly flag on session cookies.

• OPTION 5: Restricting the web server to only accept requests from specific IP addresses.

CORRECT ANSWER: OPTION 2

CORRECT ANSWER EXPLANATION: The Synchronizer Token Pattern is the industry standard for CSRF defense. Because an attacker can force a victim's browser to send a request, but cannot read the response (due to SOP) or predict a unique, hidden token, they cannot include the required valid token in their malicious request.

WRONG ANSWERS EXPLANATION:

• OPTION 1: Referer headers can be stripped by privacy software, proxies, or older browsers, making this check unreliable as a primary defense.

• OPTION 3: Using GET for state-changing operations is a major security flaw; it makes CSRF easier and exposes sensitive data in browser history and logs.

• OPTION 4: The HttpOnly flag prevents XSS from stealing the cookie via JavaScript, but it does nothing to stop CSRF, as the browser automatically includes the cookie in the forged request.

• OPTION 5: IP restriction is impractical for public web applications where users access the site from rotating or shared IP addresses.

QUESTION 2

Which Content Security Policy (CSP) directive is specifically designed to restrict where a form can submit its data, thereby mitigating certain types of data exfiltration and UI redressing?

• OPTION 1: script-src

• OPTION 2: connect-src

• OPTION 3: form-action

• OPTION 4: frame-ancestors

• OPTION 5: default-src

CORRECT ANSWER: OPTION 3

CORRECT ANSWER EXPLANATION: The form-action directive restricts the URLs which can be used as the target of a form submission from a given context. This prevents an attacker from injecting a malicious form that sends user input to their own server.

WRONG ANSWERS EXPLANATION:

• OPTION 1: script-src specifies valid sources for JavaScript, but does not control form submission targets.

• OPTION 2: connect-src restricts the URLs which can be loaded using script interfaces like Fetch or XHR, but it does not govern standard HTML form actions.

• OPTION 4: frame-ancestors specifies valid parents that may embed a page, used primarily to prevent Clickjacking.

• OPTION 5: default-src is a fallback for other directives, but form-action does not fall back to default-src in many CSP implementations, requiring explicit definition.

QUESTION 3

In the context of DOM-based XSS, which of the following JavaScript properties is considered a "Sink" that can lead to script execution if user-controlled data is assigned to it?

• OPTION 1: location. href

• OPTION 2: innerText

• OPTION 3: textContent

• OPTION 4: console. log

• OPTION 5: document. getElementById

CORRECT ANSWER: OPTION 1

CORRECT ANSWER EXPLANATION: location. href is an execution sink because assigning a javascript: URI to it will cause the browser to execute the code. For example, location. href = "javascript:alert(1)" results in an XSS vulnerability.

WRONG ANSWERS EXPLANATION:

• OPTION 2: innerText treats the input as raw text and does not parse HTML, making it a safe way to handle user input.

• OPTION 3: textContent is similar to innerText; it serves as a safe method to insert text without triggering the HTML parser.

• OPTION 4: console. log simply prints data to the developer console; while it might reveal data, it does not execute scripts in the context of the page.

• OPTION 5: document. getElementById is a selector used to find elements; it is not a sink where data is processed or executed.

Start Your Journey Today

Welcome to the best practice exams to help you prepare for your JavaScript Security (XSS, CSRF, CSP) - Practice Questions.

• You can retake the exams as many times as you want to achieve 100% mastery.

• This is a huge original question bank curated by security experts.

• You get support from instructors if you have questions regarding specific logic or edge cases.

• Each question has a detailed explanation to ensure you learn from your mistakes.

• Fully mobile-compatible with the Udemy app for learning on the go.

• 30-days money-back guarantee if you're not satisfied with the quality of the content.

We hope that by now you're convinced! There are hundreds more questions waiting for you inside the course.