For a while now, I've noticed that if I have a YouTube video active in Chrome when I install a security update, my Mac will start playing that video before about 20 seconds before the login screen appears. If I have multiple windows each with a YouTube video in them, they all start playing before I've logged in.
Why does this happen, and (besides making sure none of my Chrome windows are in YouTube video tabs when I reboot) how can I make it not happen? It seems like a potential security issue for anything to be happening with my user account before I actually enter my password.
I filmed my laptop doing this, because it's such surprising behaviour: https://www.youtube.com/watch?v=LVvu94g3iq0