CKS Minimize Microservice Vulnerabilities Practice Question
You have created a ValidatingWebhookConfiguration to reject pods without resource limits. When you try to create a pod without limits, it is created successfully. What is the most likely reason?
⚠ Common exam trap
Candidates may incorrectly assume the ValidatingWebhookConfiguration is misconfigured (e.g., missing objectSelector or wrong failurePolicy) when the actual issue is that the webhook backend service is unreachable. In Kubernetes, if the API server cannot reach the webhook server, the failurePolicy (default Ignore) allows the pod creation, so the pod passes through without validation. This is a common pitfall where the webhook service itself is not running or not accessible, rather than a configuration error.
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
✓
The webhook service is not running or is unreachable
The most likely reason a pod without resource limits is created successfully despite a ValidatingWebhookConfiguration is that the webhook service itself is not running or is unreachable. When the API server cannot contact the webhook endpoint, the default behavior (failurePolicy: Ignore) allows the request to proceed, so the pod is created without validation. If the webhook were functioning correctly, it would reject the pod; thus, the failure to reject indicates a connectivity or service issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The webhook is not matching the namespace labels
Why it's wrong here
If the webhook does not match the namespace, it would not intercept the request, but the question implies the webhook is intended to apply cluster-wide.
- ✓
The webhook service is not running or is unreachable
Why this is correct
If the webhook service is down, the API server will fail open (depending on failurePolicy) and allow the pod creation.
- ✗
The webhook is configured with failurePolicy: Fail
Why it's wrong here
failurePolicy: Fail would cause the API server to reject the request if the webhook cannot be reached.
- ✗
The pod is being created by a controller like a Deployment
Why it's wrong here
Webhooks apply to all API requests, regardless of the creator.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKS practice question is part of Courseiva's free CNCF 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 CKS exam.