CEH Web Application and Injection Attacks Practice Question
An attacker intercepts a request and notices that the server reflects the value of the 'User-Agent' header in the response without sanitization. The attacker crafts a payload that triggers an alert box. This is an example of:
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reflected XSS
Reflected XSS occurs when the application immediately returns the user input in the response; here, the User-Agent header is reflected.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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HTTP header injection
Why it's wrong here
HTTP header injection involves an attacker inserting CRLF sequences into user-supplied input to add or modify HTTP headers in the server's response. While it can lead to various issues like cache poisoning or session fixation, it is distinct from XSS, which focuses on injecting executable client-side scripts into the HTML body. The vulnerability described specifically details script execution within the response content, not header manipulation.
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DOM-based XSS
Why it's wrong here
DOM-based XSS occurs entirely on the client-side, where malicious script is executed due to the manipulation of the Document Object Model (DOM) by client-side scripts, often involving JavaScript. The server does not directly reflect the malicious payload in its HTTP response; instead, the vulnerability arises from unsafe handling of data within the browser itself. This type of XSS does not require server-side interaction for the payload to be introduced into the page's source.
- ✗
Stored XSS
Why it's wrong here
Stored XSS, also known as Persistent XSS, involves the attacker injecting a malicious script that is permanently saved on the target server, typically in a database or file system. This stored payload is then delivered to unsuspecting users when they request the affected content, causing their browsers to execute the script. The scenario described, where the input is merely reflected in a single response, does not involve the persistence characteristic essential to stored XSS.
- ✓
Reflected XSS
Why this is correct
Reflected XSS occurs when an attacker's malicious script, typically delivered via a URL parameter or HTTP header, is immediately echoed back by the web server in its HTTP response without proper sanitization. The victim's browser then interprets and executes this script as part of the legitimate page content. This non-persistent attack requires the victim to click a specially crafted link or visit a malicious site that sends the crafted request, making it a single-request, single-response vulnerability.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CEH practice question is part of Courseiva's free EC-Council certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CEH exam.