Android 12 unknown system status bar symbol:Pixel 4a

I updated my Pixel 4a to Android 12 a few days ago. Today, all of a sudden, I saw this screen like symbol on the right side of status bar, which wasn't present after updating. It is not app related because it can be seen in [tag:safe-mode] also. There is nothing in the notification bar that corresponds to this symbol. Strangely, Google search didn't help. Nobody else seems to have this problem. Any idea what this symbol means and how to get rid of it?