UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36

Steps to reproduce the problem:
1. Go to leumi.co.il in a new window (not really necessary).
2. Log into your bank account.
3. Create a new tab in the same window (not really necessary) and switch to it.
3. Go to another window.
4. Wait about sixteen minutes.

What is the expected behavior?
No popup.

What went wrong?
A "the session is about to time out, should we keep you signed in?" confirmation popup (not confirm(), a real popup window).

Did this work before? No 

Chrome version: 52.0.2743.82  Channel: stable
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: 

While this is perhaps a good use case of a popup, malware may catch up with this technique and use it for their malicious pleasures.

Note - this is not using Flash (or at least, not Flash itself, because I keep it disabled unless I need it, not "Click to play", but completely disabled using about:plugins).