This CKS practice question tests your understanding of supply chain security. 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.
An organization uses a GitOps workflow with Argo CD to deploy applications to Kubernetes. The security team wants to ensure that container images are immutable and signed. They currently use a private container registry (Harbor) with vulnerability scanning and Cosign for signing. Which combination of controls best enforces that only signed and scanned images are deployed?
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
✓
Enable Harbor's content trust feature to reject unsigned images, and use a Kyverno admission rule to verify Cosign signatures at deploy time.
Option D is correct because it enforces a two-layer defense: Harbor's content trust rejects unsigned images at the registry level, and a Kyverno admission rule verifies Cosign signatures at deploy time. This ensures that even if an unsigned image bypasses the registry, it will be blocked by Kubernetes admission control, providing defense in depth for supply chain security.
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.
✗
Configure Argo CD to verify Cosign signatures before syncing the application.
Why it's wrong here
Argo CD does not have built-in Cosign verification.
✗
Use imagePullSecrets in Kubernetes to ensure only Harbor images are used.
Why it's wrong here
Does not verify signatures or scanning status.
✗
Add a Cosign verification step in the CI pipeline before pushing images to Harbor, and rely on that guarantee.
Why it's wrong here
Does not protect against direct pushes to the registry.
✓
Enable Harbor's content trust feature to reject unsigned images, and use a Kyverno admission rule to verify Cosign signatures at deploy time.
Why this is correct
Harbor blocks unsigned pushes, and Kyverno validates signatures at admission.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the concept that imagePullSecrets only handle authentication, not integrity or signing, leading candidates to mistakenly choose Option B as a security control.
Detailed technical explanation
How to think about this question
Harbor's content trust uses Notary to enforce that only signed images are pushed, leveraging TUF (The Update Framework) for metadata. Kyverno's verifyImages rule uses Cosign to check signatures against a public key or keyless Sigstore, intercepting the pod creation request via a MutatingAdmissionWebhook. In a real-world scenario, a compromised CI pipeline could push unsigned images to Harbor, but content trust would reject them, and even if content trust were misconfigured, Kyverno would block the deployment.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CKS question in full detail.
Supply Chain Security — This question tests Supply Chain Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable Harbor's content trust feature to reject unsigned images, and use a Kyverno admission rule to verify Cosign signatures at deploy time. — Option D is correct because it enforces a two-layer defense: Harbor's content trust rejects unsigned images at the registry level, and a Kyverno admission rule verifies Cosign signatures at deploy time. This ensures that even if an unsigned image bypasses the registry, it will be blocked by Kubernetes admission control, providing defense in depth for supply chain security.
What should I do if I get this CKS 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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