ProfileGrid < 5.9.9.8 - Unauthenticated Privilege Escalation via Unrestricted Group ID

The ProfileGrid WordPress plugin before 5.9.9.8 does not restrict which group an anonymous visitor may register into through its front-end registration, allowing unauthenticated users to register directly into a privileged group and be granted that group's configured role, up to Administrator when such a group exists, leading to privilege escalation.