SAML Single Sign On < 5.4.4 - Unauthenticated Authentication Bypass via SAMLResponse Parameter Signature Algorithm Confusion

Description

The plugin is vulnerable to Authentication Bypass via SAML Signature Algorithm Confusion. The vulnerability exists because Mo_SAML_Utilities::mo_saml_cast_key() reads the SignatureMethod Algorithm attribute directly from the attacker-controlled SAMLResponse parameter rather than enforcing the locally configured algorithm, causing the plugin to recast the IdP's RSA public key as an HMAC-SHA1 shared secret and validate the forged signature against it. This makes it possible for unauthenticated attackers to forge a SAML assertion targeting any WordPress account — including administrators — obtain valid WordPress authentication cookies, and achieve full administrator-level account takeover.