Whoops, we forgot to tell you there is a microphone. Google's most recent Nest integration lets you use the security system with the Google virtual assistant but the company forgot to disclose that Nest has a microphone capable of listening. There is nothing in any of the product material disclosing that the alarm keypad and motion sensor component has a microphone.
Google told Business Insider that it never used the microphone to record anything, never intended it to be a secret and users can turn it off. Google says not disclosing it was an error and that the mic is there so to access future features.