The Grandstream VoIP products deploy a remote provisioning mechanism that allows to automatically set configuration elements on phone/app startup. By default, an insecure connection to `fm.grandstream.com` is used to obtain the provisioning profile. An active attacker can redirect this request and change arbitrary values of the configuration. This allows to redirect phone calls through a malicious server, turn the phone into a bug, change passwords, and exfiltrate system logs (including the phone numbers dialed by the user).