I have a habit of muttering about people in quite disparaging ways when I think I'm on mute.
It's going to backfire one of these days.

I did mutter "you would say that ya fucking cunt" in a previous job when the CEO was giving some kind of update before discovering the mute button was quite definitely off.
He definitely heard it because he kind of paused and looked a bit startled. I don't think he knew it was me.
I was being made redundant anyway.
I saw some of the HR officers laughing, so I kind of won that one.