The answer is Insecure Direct Object Reference (IDOR). This is correct because IDOR vulnerabilities occur when an application exposes internal object references—such as user IDs—and fails to verify authorization, allowing an attacker to manipulate those references directly. When the server returns different page sizes, response times, or content for valid versus invalid IDs, it provides a reliable side-channel for enumerating legitimate objects, which is a classic detection method for IDOR. On the Certified Ethical Hacker CEH exam, this scenario tests your ability to recognize IDOR as an access control flaw distinct from injection or broken authentication; a common trap is confusing it with parameter tampering, but the key differentiator is the direct reference to an internal object. Remember the memory tip: "Different responses, direct references—IDOR detects the difference."
CEH Web Application and Injection Attacks Practice Question
This CEH practice question tests your understanding of web application and injection attacks. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A security analyst notices that a web application returns different page sizes when a valid user ID is submitted versus an invalid one in the URL parameter. Which type of vulnerability is most likely being exploited?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Insecure Direct Object Reference (IDOR)
This is a classic indicator of an Insecure Direct Object Reference (IDOR) vulnerability, where an attacker can enumerate valid IDs by observing differences in responses.
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.
✗
Stored Cross-Site Scripting (XSS)
Why it's wrong here
XSS involves injecting scripts into web pages, not manipulating IDs to see different responses.
✓
Insecure Direct Object Reference (IDOR)
Why this is correct
IDOR occurs when an application exposes internal object references (e.g., user IDs) and allows unauthorized access by modifying them.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Cross-Site Request Forgery (CSRF)
Why it's wrong here
CSRF does not involve direct enumeration via parameter manipulation.
✗
SQL Injection
Why it's wrong here
While SQL injection can cause different responses, the described behavior (valid vs. invalid ID) is more typical of IDOR.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Web Application and Injection Attacks — This question tests Web Application and Injection Attacks — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Insecure Direct Object Reference (IDOR) — This is a classic indicator of an Insecure Direct Object Reference (IDOR) vulnerability, where an attacker can enumerate valid IDs by observing differences in responses.
What should I do if I get this CEH question wrong?
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. During a penetration test, a security analyst discovers that a web application uses sequential numeric identifiers in URLs (e.g., /profile?id=100). By modifying the id parameter, the analyst can access another user's profile data without authorization. Which vulnerability is being exploited?
medium
A.SQL injection
✓ B.Insecure Direct Object Reference (IDOR)
C.Server-Side Request Forgery (SSRF)
D.Cross-Site Request Forgery (CSRF)
Why B: IDOR (Insecure Direct Object Reference) occurs when an application exposes internal object references (e.g., database keys) and fails to enforce proper access controls, allowing users to manipulate them to access unauthorized data.
Variation 2. During a web application penetration test, a security analyst intercepts a request using Burp Suite and notices the following parameter in the URL: /profile?user_id=123. By changing the user_id to 124, the analyst is able to view another user's profile. Which vulnerability is being exploited?
medium
A.SQL Injection
B.Cross-Site Scripting (XSS)
✓ C.Insecure Direct Object Reference (IDOR)
D.Cross-Site Request Forgery (CSRF)
Why C: IDOR occurs when an application exposes a direct reference to an internal object (like a user ID) without proper authorization checks, allowing unauthorized access.
Last reviewed: Jun 21, 2026
Question Discussion
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