Okay-this may sound like a stupid question.But,I’ve been wondering about it for quite some time now and I just finally have to ask…when I see those little Avast pop-ups telling me that Avast has blocked a potential threat,am I correct in assuming that that pop-up is for the page that is currently opened (or opening) or,could it be for another page (tab) that I also have open but I am not currently viewing ?
I’m thinking that it’s the former.I’ve been experiencing some issues at times within Yahoo mails spam folder.Sometimes,(I don’t even have to open any of the mail.All I have to do is open the spam folder itself) Avast is alerting me that it has blocked a potential threat as soon as I open the spam folder in Yahoo mail.
It can be for any page you have open.
It can even be for a page that you don’t have open if your system is infected.
I suggest you follow the instructions:
https://forum.avast.com/index.php?topic=53253.0
Better safe than sorry 
Try and capture a screenshot of the avast alert and attach it to your next post.
If you haven’t rebooted or had another avast message, right click the avast tray icon and select ‘Show last popup message.’