Try restore your home page:

• How to set the home page

Try go to about:config search for browser.startup.homepage change its value to:

about:home - default
about:blank - blank page
url - type a link that you want

• about:config

Also:

• Firefox in safe mode
• Problems caused by malwares
• Preferences won’t save
• http://kb.mozillazine.org/Preferences_not_saved
• Reset Firefox

This issue can be caused by the MySearchDial extension.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can also check if you have a user.js file in the profile folder to initialize prefs each time Firefox starts.

The user.js file is only present if you or other software has created this file and normally it wouldn't be there. You can check its content with a plain text editor (right-click: Open with) if you didn't create this file yourself.

The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

• http://kb.mozillazine.org/Preferences_not_saved

I found MySearchDial extension open. I removed it and the "extra" tab does not open now.