The System Details list shows the Honey extension and this extension has been reported to make Firefox responding slow. See also its reviews.

• https://addons.mozilla.org/en-US/firefox/addon/honey/reviews/

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Why is Honey affecting performance on Firefox 60 now?

With the Honey add-on running prior to the upgrade to 60, there were no issues. I used Honey in Firefox 58 and 59 with no performance issues.

What changed?

I have know idea why Honey isn't performing very well. This is an issue that its creator needs to address in an update. If you looked at the reviews then you can see that you are not the only one and there are several SUMO threads where users reported issues that could be tracked to this extension. you will have to disable this extension if you want to restore full speed.

• https://support.mozilla.org/en-US/search/advanced?q=honey&asked_by=&answered_by=&w=2&a=1&sortby=1

the firefox update to version 60.0.1 that just got released should fix this problem.