Hi I am using firefox Version 51.0.1 and faced the similar issue. The property which I used to get back the Firepath and Firefinder under firebug is =
browser.tabs.remote.autostart.2 = false
Steps:
- Open firefox
- Type about:config in the explorer
- click on the I uderstand button
- Now in the search box enter "browser.tabs.remote.autostart.2" (without quotes) and hit enter
- Set the value as false ( you need to click the property to toggle the values)
- close the firefox and open again
- Launch firebug ...Now you should see your fire path and firefinder back