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CAS-004 Practice Question: During a penetration test, an engineer discovers…
During a penetration test, an engineer discovers that the application uses client-side JavaScript to validate input before submission. What is the MOST significant vulnerability?
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
✓
Server-side validation is missing
Client-side validation can be easily bypassed by disabling JavaScript or sending crafted HTTP requests. Without server-side validation, attackers can submit malicious payloads, leading to injection attacks. XSS and IDOR are separate issues; weak session management is unrelated to input validation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Server-side validation is missing
Why this is correct
The lack of server-side validation allows any client-side validation to be bypassed, creating a serious vulnerability.
- ✗
Cross-site scripting
Why it's wrong here
XSS is one potential outcome, but the root cause is missing server-side validation.
- ✗
Insecure direct object reference
Why it's wrong here
IDOR is an authorization issue, not directly related to input validation.
- ✗
Weak session management
Why it's wrong here
Session management is a separate security concern not indicated by client-side validation.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.