I started a topic a while ago that had some good info.

https://pinside.com/pinball/forum/topic/wifi-enabled-smart-plugs

Wi-Fi can be hacked by capturing the key and decrypting it offline. You can sit in a parking lot to do it which what happened to Macys a about 13 years ago. Macys wasn't even encrypting the key which made it even easier. I cant remember how many customers credit cards and data were exposed in that hack. Once you're in on the network you can snoop around for devices and their vulnerabilities to hack them. The hackers can be "quiet" in how aggressive they scan the network. Unless you have some sort of network intrusion detection system to monitor malicious traffic you probably wouldn't even notice.

Hell, some people have their phones and wireless devices set to join networks automatically which can get you hacked. As an experiment a guy built a device and shipped it from his house to Defcon (hacker conference in Vegas). He picked up the device where it snooped and collected all kinds of cellular/customer data from passengers on the flight it was shipped on. He presented his findings at the conference.