I was going to post the same subject at the weekend. Only on PPRuNe email, same pop-ups. And I'm using Linux!
If I click the pop-up to cancel, the whole email page crashes out and I have to log in again. It usually happens three times before the page stabilises and I can read email.
Using Linux, I can't download and run a Windows executable. For me it's a problem in PPRuNe.