This CCSP practice question tests your understanding of cloud application security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which of the following is the best way to protect a web application from cross-site scripting (XSS) attacks?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a combination of input validation, output encoding, and Content Security Policy.
Option C is correct because cross-site scripting (XSS) attacks exploit multiple vectors, and no single defense is sufficient. Input validation prevents malicious payloads from being stored or processed, output encoding ensures that any residual dangerous characters are rendered inert in the HTML context, and Content Security Policy (CSP) provides a robust, browser-enforced layer that can block inline scripts and restrict script sources even if other defenses fail. This defense-in-depth approach aligns with the OWASP XSS prevention cheat sheet and is the recommended strategy for cloud-hosted web applications.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Encode all output that is rendered in HTML.
Why it's wrong here
Output encoding is critical but insufficient without input validation and CSP.
✗
Implement a Content Security Policy (CSP) as the sole defense.
Why it's wrong here
CSP is a strong layer but can be bypassed; it should be combined with other measures.
✓
Use a combination of input validation, output encoding, and Content Security Policy.
Why this is correct
Defense in depth reduces the risk of XSS.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Validate all user input on the server side.
Why it's wrong here
Input validation helps but does not prevent all XSS; output encoding is also needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that a single security control (like output encoding or CSP alone) is sufficient, when the correct answer always requires a defense-in-depth combination of input validation, output encoding, and CSP.
Trap categories for this question
Command / output trap
Output encoding is critical but insufficient without input validation and CSP.
Detailed technical explanation
How to think about this question
Under the hood, output encoding must be context-aware: HTML entity encoding (e.g., `<` for `<`) works for HTML body contexts, but JavaScript contexts require backslash escaping or Unicode escapes, and URL contexts require percent-encoding. CSP works by delivering an HTTP header (e.g., `Content-Security-Policy: default-src 'self'`) that instructs the browser to restrict resource loading; however, a common subtlety is that CSP's `strict-dynamic` mode can allow trusted scripts to inject new scripts, which can be exploited if the trusted script is vulnerable. In a real-world cloud scenario, a misconfigured CSP with `'unsafe-inline'` or missing `base-uri` directive can be trivially bypassed, reinforcing why CSP must be part of a layered defense.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Cloud Application Security — This question tests Cloud Application Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a combination of input validation, output encoding, and Content Security Policy. — Option C is correct because cross-site scripting (XSS) attacks exploit multiple vectors, and no single defense is sufficient. Input validation prevents malicious payloads from being stored or processed, output encoding ensures that any residual dangerous characters are rendered inert in the HTML context, and Content Security Policy (CSP) provides a robust, browser-enforced layer that can block inline scripts and restrict script sources even if other defenses fail. This defense-in-depth approach aligns with the OWASP XSS prevention cheat sheet and is the recommended strategy for cloud-hosted web applications.
What should I do if I get this CCSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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