Question: white flash appears when restarting mac?
Recently, I had a weird problem of a random "guest user" appearing when I restarted my mac. So I decided to shutdown my mac completely and restart it to see if it was just a weird glitch after I had deleted my sister's guest account. But then I saw this weird white flash (almost like a screenshot) across my screen. I thought it was just my eyes, but when I restarted it again, the same thing happened. The guest user is now gone, but I'm worried about my mac being broken.
MacBook Pro TouchBar and Touch ID, macOS High Sierra (10.13.1)