This CKS practice question tests your understanding of supply chain security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Refer to the exhibit. A cluster has the ClusterImagePolicy shown. A developer creates a pod with an image from registry.example.com/myapp:v1, which was built and signed by a GitHub Actions workflow that is NOT defined in the policy (different workflow). Which behavior will occur when the pod is created?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "NOT"
Why it matters: Negative qualifier — you are looking for the one option that does NOT apply. Most options will be true; only one is false for this scenario.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The pod is denied because the image's signer identity does not match the policy.
Option D is correct because the ClusterImagePolicy enforces that images must be signed by a specific identity (the GitHub Actions workflow defined in the policy). The image from registry.example.com/myapp:v1 was signed by a different workflow, so the signer identity does not match the policy's required identity. Sigstore keyless signing verifies the OIDC identity embedded in the signature, and if the identity does not match the policy's `issuer` and `subject` patterns, the admission controller denies the pod.
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.
✗
The pod is admitted because keyless signing does not enforce identity matching.
Why it's wrong here
Keyless signing does enforce identities; the spec includes an identities array.
✗
The pod is admitted because the policy only applies to images with a tag 'v*'.
Why it's wrong here
The policy uses glob: registry.example.com/*, which matches all tags.
✗
The pod is admitted because the image is from the allowed registry.
Why it's wrong here
The registry is allowed, but the identity is also required to match.
✓
The pod is denied because the image's signer identity does not match the policy.
Why this is correct
The identity check fails, so cosigned denies the admission.
Clue confirmation
The clue word "NOT" 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 misconception that keyless signing only verifies the signature's cryptographic validity, not the identity of the signer, but in reality the policy enforces identity matching via OIDC claims.
Detailed technical explanation
How to think about this question
Sigstore keyless signing uses Fulcio to issue short-lived certificates binding an OIDC identity to the signature. The ClusterImagePolicy in Kubernetes (using the ImagePolicyWebhook or dynamic admission controller) evaluates the `issuer` and `subject` fields from the certificate against the policy's `required` block. If the identity does not match, the image is rejected even if it comes from an allowed registry. This prevents supply chain attacks where a compromised CI pipeline signs images with a different identity.
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: The pod is denied because the image's signer identity does not match the policy. — Option D is correct because the ClusterImagePolicy enforces that images must be signed by a specific identity (the GitHub Actions workflow defined in the policy). The image from registry.example.com/myapp:v1 was signed by a different workflow, so the signer identity does not match the policy's required identity. Sigstore keyless signing verifies the OIDC identity embedded in the signature, and if the identity does not match the policy's `issuer` and `subject` patterns, the admission controller denies the pod.
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: "NOT". Negative qualifier — you are looking for the one option that does NOT apply. Most options will be true; only one is false for this scenario.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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