The correct answer is that the firewall's root CA certificate is not installed in the user's browser trusted root store. This is the most likely reason for the browser certificate warning after SSL decryption because when a Palo Alto Networks firewall decrypts traffic using a company-issued internal PKI CA certificate, the browser must trust the root of that certificate chain to validate the firewall’s re-signed server certificates. Without that root CA in the trusted store, the browser sees an untrusted issuer and displays a warning. On the PCNSA exam, this scenario tests your understanding of SSL decryption trust architecture—specifically that decryption breaks the original certificate chain and replaces it with one the client must explicitly trust. A common trap is assuming the internal CA certificate alone is enough; the key is that the root must be deployed to every client. Memory tip: “Root the trust, or the browser will bust.”
PCNSA Decryption and Monitoring Practice Question
This PCNSA practice question tests your understanding of decryption and monitoring. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 firewall administrator notices that traffic from an internal user is being decrypted, but the user's browser shows a certificate warning. The firewall uses a CA certificate issued by the company's internal PKI. What is the most likely reason for the browser warning?
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
✓
The firewall's root CA certificate is not installed in the user's browser trusted root store.
Option B is correct because the browser warning indicates that the firewall's decrypted traffic is being signed with a certificate that the browser does not trust. When a firewall performs SSL/TLS decryption using a CA certificate from the company's internal PKI, the browser will only trust the decrypted connections if the root CA certificate of that PKI is installed in the browser's trusted root certificate store. Without this trust anchor, the browser cannot validate the certificate chain presented by the firewall, resulting in a certificate warning.
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 decryption policy has the action 'decrypt' but no certificate profile.
Why it's wrong here
A certificate profile is for client authentication, not related to server certificate warnings.
✓
The firewall's root CA certificate is not installed in the user's browser trusted root store.
Why this is correct
This is the most common cause of browser certificate warnings in forward proxy scenarios.
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.
✗
The user's browser does not support TLS 1.2.
Why it's wrong here
Cipher mismatch fails the connection, not a certificate warning.
✗
The server certificate is revoked.
Why it's wrong here
Revocation is checked by the firewall, and failure would result in a different error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse a missing trusted root CA certificate with a server certificate revocation or a decryption policy misconfiguration, failing to recognize that the browser warning specifically indicates a trust chain issue rather than a revocation or policy error.
Detailed technical explanation
How to think about this question
In SSL/TLS forward proxy decryption, the firewall generates a certificate on-the-fly for each destination server, signed by the firewall's internal CA. The browser must have the root CA certificate of that internal CA in its trusted root store to validate these dynamically generated certificates. If the root CA is missing, the browser treats the certificate as issued by an untrusted authority, triggering a warning. This is distinct from server certificate revocation, which would be checked via CRL or OCSP and produce a different error message.
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 practitioner preparing for the PCNSA 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Decryption and Monitoring — This question tests Decryption and Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall's root CA certificate is not installed in the user's browser trusted root store. — Option B is correct because the browser warning indicates that the firewall's decrypted traffic is being signed with a certificate that the browser does not trust. When a firewall performs SSL/TLS decryption using a CA certificate from the company's internal PKI, the browser will only trust the decrypted connections if the root CA certificate of that PKI is installed in the browser's trusted root certificate store. Without this trust anchor, the browser cannot validate the certificate chain presented by the firewall, resulting in a certificate warning.
What should I do if I get this PCNSA 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: "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.
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Question Discussion
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