As to the consequences of owning a product with this backdoor? Well, to make it very simple, put it this way: an attacker could take over your wireless internet, do anything they want with it (even locking you out of your own internet connection), all without your password. On a few conditions: the attacker is smart enough to run a shell script, and either has access to your ISP or is in the vincity of your WLAN network. Sure, that may be better than leaving the backdoor wide open, but… is it really necessary to leave the backdoor open just a peep?
Easter egg: DSL router patch merely hides backdoor instead of closing it
Researcher finds secret “knock” opens admin for some Linksys, Netgear routers.