ISP worker here. Our chosen routers default to an 8 digit password, the first 4 are the last 4 of the mac in hex, which anyone can easily see being broadcast by the wifi network. The last 4 are a part of a unique serial number, but its just 0-9. Ultimately, if you try to brute force this default password, you need 10000 tries. It takes a regular GPU 2 minutes with hashcat. It baffles my mind that companies think this is OK.