In my experience this is not restricted to manufacturers. Routers supplied by ISP's and carriers often have custom firmwares with have backdoors as well, of c

In my experience this is not restricted to manufacturers. Routers supplied by ISP's and carriers often have custom firmwares with have backdoors as well, of course labelled as a "Maintenance & Remote Service" feature. After figuring out the password on mine, I had no issue going into my neighbours router with full access...