hardMultiple Choice
CAS-004 Implementing single sign-on using SAML 2.0 Practice Question
A company is implementing single sign-on using SAML 2.0. A security architect is reviewing the authentication flow and notices that the identity provider (IdP) does not digitally sign the SAML assertions. Which of the following is the most significant security risk?
⚠ Common exam trap
A common mix-up: candidates confuse integrity with confidentiality: candidates often pick 'intercepted and read' because they think of encryption, but signing addresses tampering, not eavesdropping.
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 assertion could be modified in transit
SAML assertions carry the authentication and authorization claims that the service provider (SP) trusts. Without a digital signature, there is no cryptographic integrity protection, so an attacker who can intercept or manipulate the SAML response (e.g., via a man-in-the-middle or by tampering with the POST binding) can alter the assertion contents—such as changing the user identity or elevating privileges—and the SP has no way to detect the modification. This is the most significant risk because it directly undermines the trust model of SSO.
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 assertion could be modified in transit
Why this is correct
Unsigned SAML assertions let any intermediary alter attributes such as NameID or role claims before the service provider consumes them, because the SP has no cryptographic means of verifying origin or integrity. This directly satisfies the stem's constraint: without an IdP signature, tampering in transit is undetectable, enabling privilege escalation or impersonation.
- ✗
The assertion could be intercepted and read
Why it's wrong here
Unsigned assertions are still encrypted by TLS in transit, so interception for reading is not the primary consequence of a missing signature. Confidentiality controls such as TLS or XML encryption address eavesdropping; signature verification instead guarantees integrity and origin of the assertion.
- ✗
The IdP could be spoofed
Why it's wrong here
Signing helps verify the IdP's identity, but without signing, an attacker could also spoof the IdP; however, modification is the more direct risk.
- ✗
The assertion could be replayed
Why it's wrong here
Without a signature, an attacker can alter the assertion's subject or attributes and the service provider cannot detect tampering, enabling forged authentication or privilege escalation. Replay is mitigated separately by NotOnOrAfter, InResponseTo and audience conditions, which remain effective regardless of signing.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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