- A
Require a specific sts:ExternalId value in the role trust policy in Account A.
A trust policy condition on sts:ExternalId is the standard confused-deputy protection for third-party role assumption. It ensures that only callers who know the shared external identifier can assume the role.
- B
Make sure the vendor includes that same ExternalId when calling sts:AssumeRole.
The caller must supply the exact ExternalId value that the trust policy expects. If the value is missing or different, STS denies the AssumeRole request.
- C
Share long-term access keys from Account A with the vendor.
Why wrong: Long-term credentials increase risk and are not needed for third-party access. STS temporary credentials are the secure mechanism for this scenario.
- D
Attach a permissions boundary to the role to satisfy the ExternalId requirement.
Why wrong: Permissions boundaries limit what the role can do after it is assumed. They do not validate who may assume the role and do not protect against confused deputy attacks.
- E
Allow sts:GetSessionToken instead of sts:AssumeRole in the trust policy.
Why wrong: GetSessionToken is not the cross-account role-assumption mechanism used for third-party access. The correct approach is sts:AssumeRole with an ExternalId condition.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 software vendor in Account B must assume a role in Account A to process support tickets. Security wants to prevent confused deputy attacks. Which two configurations are required for this access pattern to work safely? Select two.
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
Require a specific sts:ExternalId value in the role trust policy in Account A.
Option A is correct because requiring a specific sts:ExternalId value in the role trust policy in Account A is a standard AWS mechanism to prevent the confused deputy problem. The ExternalId acts as a unique secret that the vendor must provide when assuming the role, ensuring that the role is assumed only for the intended purpose and not by a malicious third party.
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.
- ✓
Require a specific sts:ExternalId value in the role trust policy in Account A.
Why this is correct
A trust policy condition on sts:ExternalId is the standard confused-deputy protection for third-party role assumption. It ensures that only callers who know the shared external identifier can assume the role.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Make sure the vendor includes that same ExternalId when calling sts:AssumeRole.
Why this is correct
The caller must supply the exact ExternalId value that the trust policy expects. If the value is missing or different, STS denies the AssumeRole request.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Share long-term access keys from Account A with the vendor.
Why it's wrong here
Long-term credentials increase risk and are not needed for third-party access. STS temporary credentials are the secure mechanism for this scenario.
- ✗
Attach a permissions boundary to the role to satisfy the ExternalId requirement.
Why it's wrong here
Permissions boundaries limit what the role can do after it is assumed. They do not validate who may assume the role and do not protect against confused deputy attacks.
- ✗
Allow sts:GetSessionToken instead of sts:AssumeRole in the trust policy.
Why it's wrong here
GetSessionToken is not the cross-account role-assumption mechanism used for third-party access. The correct approach is sts:AssumeRole with an ExternalId condition.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the ExternalId with a permissions boundary or think that long-term keys are acceptable for cross-account access, but the correct answer requires both the trust policy condition and the caller's inclusion of the ExternalId in the API call.
Trap categories for this question
Similar concept trap
Permissions boundaries limit what the role can do after it is assumed. They do not validate who may assume the role and do not protect against confused deputy attacks.
Scenario analysis trap
Long-term credentials increase risk and are not needed for third-party access. STS temporary credentials are the secure mechanism for this scenario.
Detailed technical explanation
How to think about this question
The confused deputy problem arises when a downstream service (the vendor) is tricked into assuming a role in another account on behalf of an unintended principal. AWS mitigates this by requiring an sts:ExternalId in the trust policy, which the calling entity must include in the AssumeRole API call. The ExternalId is not a secret like a password but a unique identifier that ties the role assumption to a specific business context, such as a support ticket ID or a customer account number.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Require a specific sts:ExternalId value in the role trust policy in Account A. — Option A is correct because requiring a specific sts:ExternalId value in the role trust policy in Account A is a standard AWS mechanism to prevent the confused deputy problem. The ExternalId acts as a unique secret that the vendor must provide when assuming the role, ensuring that the role is assumed only for the intended purpose and not by a malicious third party.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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