Why is my screen turning black within the window of Safari & Mail app? It seems to be spreading! a virus?

Hi mr Hoffman,

No, I don’t have it on Dark Mode setting. I wish I had taken a screen shot to show it, No one else I’ve talked to has experienced it. The only part that turned black was the window within the app, as if someone decided to ‘fill’ the message square window in solid black (within Mail). Around the window, everything else looks normal.

To John,

This seems to have solved my issues! Thank you! I still don't know what happened, but I am writing from my computer and have not experienced further problems.

I had forgotten that booting in Safe Mode includes a "basic check of your startup disk similar to using First Aid Disk Utility..." and that it is "useful when you're trying to resolve and issue that doesn't seem to be associated with using any particular app".

I will remember to try this first next time.

Thank you for your time and follow up. S

Ok. I didn't think so, but I've never seen this, I'm stumped! I'll try booting on safe mode. Thank you for your reply.

Ok. I'll report back once I've retried today.

So far no issues in safe mode, which is great. It did ask me to log in twice, but no glitches. I'm going to restart my computer now in normal mode and see if it reoccurs.