🛡️ Security

Assertion Consumer Service (ACS)

The endpoint on a SAML service provider that receives the signed SAML response from the identity provider and establishes the user's session. It accepts HTTP POSTs from any client by design, which makes its XML parsing pre-authentication attack surface.

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How a SAML Login Flow Works and Where an Unauthenticated Request Gets Parsed

A SAML gateway must parse attacker-controlled XML before it can verify any signature. Here is the login flow step by step and the exact points where anonymous input reaches the parser.

intermediate 6 min read

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