OAuth Single Sign On – SSO (OAuth Client) < 7.1.3 - Unauthenticated Authentication Bypass

Description

The OAuth Single Sign On – SSO (OAuth Client) plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 7.1.2. This is due to missing enforcement of the email-verification claim when the claim is absent from the IdP response, because the old inline check was gated on isset($resource_owner[$idp_email_verified_key]) and skipped silently when the claim was not present. This makes it possible for unauthenticated attackers to gain access to an account without a verified email address by authenticating through an OAuth provider that omits the email-verification claim from its response, causing the verification check to be silently bypassed. The 'email verified' check must be enabled in the plugin settings (mo_oauth_email_verify_check).