Site popping up some member login on Firefox

So for the past several weeks I’ve noticed that my site has been popping up a strange login box that says:

“Authentication Required”
“Enter Username and password for ftp://(my host site name).”

https://grrrltraveler.com

This can be whether I’m logged in as admin or not. Have I been hacked or have I accidentally ticked a box in settings? I have never had this problem before and it seems suspicious. As a result, my traffic has gone down considerably as well.

Any ideas how to remedy this?

Thanks in advance.