A couple of weeks ago, Netgear announced that there is a major security vulnerability in several router models that allows anyone within range of your wireless network to log in as administrator without credentials. So many things can go wrong if this happens to you. Even the US-CERT recommends that you don't use the router until you've updated it.
Check your home wireless router. Popular brands include Linksys, Asus, D-Link and Netgear, among others. If your manufacturer is Netgear, check which version you have and update your router with newer firmware asap.
The page listing the models and the steps to update the firmware is here: http://kb.netgear.com/000036386/CVE-2016-582384.
Even if you don't have a Netgear router, it is always a good idea to log in to your router occasionally to see if it needs a firmware update. Or set a Google alert that queries the manufacturer's name and model. Add the word "firmware" to your query and configure it to deliver a notification to you whenever there is new information available on the Internet.
For more information, see the Forbes article here: http://www.forbes.com/sites/leemathews/2016/12/12/these-netgear-routers-are-scarily-easy-to-hijack/#1f89ad0d9537.