I have only seen a single appearance of what I described. The lack of subsequent appearances might mean that it was an aberration.
When a 'caution' signal is displayed in the system tray Avast icon, it should be attended to without delay. It might indicate that a shield is down or another malfunction which is impairing the protection given by Avast. I am on constant alert to the possibility of security incidents. To show this caution signal without proper cause is to mess the user around and so make her/him more vulnerable to social engineering.
The blue spot would reasonably be taken as a low priority information alert and I am now accustomed to that
I regret not having had the presence of mind to capture the screen image of the 'aberration'. If it happens again, I will pounce on it.
