Guest hacked my WiFi and Nest system

[Patrick1781]

I had guests stay at our place for two weeks. The day before they were leaving I had to meet he town there to replace our water meter and found my Nest system and WiFi had been hacked by the guest, He never asked about changing the temperature and never reported any problems. AirBnB says if there is an issue contact the host; he never did. He just hacked into my system and played God. It makes me want to get off AirBnB,

Any suggestions for dealing with this? 

[Steven65]

How was it hacked? I also have a NEST and would be good to know vulnerabilities. I understand Nest now have 2 factor authentication which should fix your problem.