“A few days after installing the NAS, I discovered I could access the NAS using my public IP, even though I hadn’t port forwarded anything!”
The Terramaster quietly punched four holes through the router with UPnP, including its admin page. There was no setting to stop it. Change the port and it opened the new one without closing the old. Six weeks after the report, Terramaster still had no fix. The workaround was hand editing a JSON file over SSH.