GHSA-C3M2-JQMQ-PVP3 authentik's XML Signature Wrapping in SAML Source ACS allows authentication as arbitrary federated user

Summary authentik's SAML Source ACS endpoint is vulnerable to XML Signature Wrapping when validating upstream SAML responses. An attacker with any account at the upstream IdP can reuse a valid signed assertion to authenticate as another federated user. Patches authentik 2026.5.1, 2026.2.4 and...