In a home network you typically have a router that separates your LAN (local area network) from the internet and shares one public IP among the devices in your network; in that case you have little to worry about. You can tell by the kinds of IP addresses your devices have: if it starts with 192.168.x.y, 172.x.y.z, or 10.x.y.z, then it's not reachable from the internet. The problem with these printers is that on their network there's no such separation and they are listening on a publicly routed IP address, but they've been designed with the tacit assumption that they will be used on a secured network.