I just started using Firefox Quantum (57.0.4). 1password is working normally, except that I got a message in the browser when having it try to put the credentials into a log in form, and it said, "A script in 1password is causing Firefox to slow down."
The site it did this on is http://www.sedo.com. It eventually inserted the credentials, but it took about 6-7 seconds to begin doing so. Funny thing is, when I was using Chrome until today, even there I was noticing that for Sedo.com it also took a very long time before the credentials were placed into the fields. So, it sounds like a 1password bug, not Firefox--it's only that Firefox issues a warning message to me.
1Password Version: 6.8.5
Extension Version: 188.8.131.52
OS Version: MacOS 10.13.2
Sync Type: Not Provided