Advisories for Npm/@Better-Auth/Sso package

The SSO plugin's POST /sso/register endpoint lets any member of an organization attach a new SSO provider to that organization. It checks that the caller has a membership row, but it does not check whether the caller has an administrative role for the organization. This creates an authorization mismatch for the same resource. Other org-linked SSO provider management endpoints treat those providers as admin-managed: list, get, update, and delete require …

The @better-auth/sso plugin's POST /sso/register endpoint accepts attacker-controlled oidcConfig.userInfoEndpoint, tokenEndpoint, and jwksEndpoint URLs when skipDiscovery: true is set, persists them on the ssoProvider row without origin validation, then issues server-side fetches to those URLs during the OIDC callback. The fetched response body is reflected through the user profile, producing a non-blind SSRF reachable by any authenticated session. The same primitive exists on POST /sso/update-provider.