Firefox started getting very slow recently. Scrolling, typing gets delayed, rainbow rotator appears here and there. Not sure of exact moment: either after FF update or 1Password update.
The issue goes away if I disable the 1Password extension and restart the browser just in case. FireFox now runs promptly again.
Enabling the 1Password extension resumes the problem.
Other installed extension is AdBlock Plus. Maybe they are conflicting in some way as both manipulate DOM?
Mozilla FireFox 56.0, OS X 10.11.6 El Capitan, 1Password extension 220.127.116.11, AdBlock Plus extension 2.9.1
1Password Version: 6.8.2 (682003)
Extension Version: 18.104.22.168
OS Version: OS X 10.11.6 El Capitan
Sync Type: Dropbox
Referrer: forum-search:firefox slow