It makes a great headline but in reality a WIFI enabled appliance is essentially a laptop attached to said appliance running some flavor of Linux in most cases. Its an excellent hack because most people would never suspect the fridge or toaster being used as an entry point into their home network. TV sets, printers, scanners, wifi thermostats can all be hacked and placed in the retail packaging for an unsuspecting consumer to bring home.
If the WiFi router is password protected the hacked refrigerator or other device cannot access it unless/until the homeowner brings it into his network via entering the password into the device’s interface. Until then the infected device is blind to the world.
So really it’s looking for unsecured access points. -Just like every other hacker out there.