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AWS singlesignon medium security documentation change

Service: singlesignon · 2026-07-04 · Security-related medium

File: singlesignon/latest/userguide/other-idps.md

Summary

Added requirement for SAML assertion's NameID to exactly match IAM Identity Center usernames.

Security assessment

Documents authentication failure conditions that could prevent account takeover if mismatched. Explicitly states sign-in failures when NameID doesn't match provisioned usernames, addressing potential authentication bypass risks.

Diff

diff --git a/singlesignon/latest/userguide/other-idps.md b/singlesignon/latest/userguide/other-idps.md
index 4ea98eedf..86105b6c6 100644
--- a//singlesignon/latest/userguide/other-idps.md
+++ b//singlesignon/latest/userguide/other-idps.md
@@ -25,0 +26,2 @@ Any identity provider (IdP) that implements these standard protocols is expected
+    * The SAML assertion's `Subject` `NameID` value must exactly match the **Username** of a user provisioned in IAM Identity Center. Sign-in fails if IAM Identity Center cannot match the `NameID` to a **Username** , even when the external IdP authenticates the user successfully.
+