Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Hi Wesley, Thanks for responding. The problem doesn’t occur in safe mode. I tried the troubleshooting section and turned off the 'Use Hardware acceleration when available', restarted Firefox and the problem is still there. The only change I have noticed since I installed Firefox (it’s a new PC) is now when I open a new tab and type something in the search box, I get this 'www.safesear.ch/' site and it may be that as the problem does not appear in Internet explorer or on my laptop and they do not have this safesearch coming up. Trouble is I can’t get rid of it, it’s not in the add/remove programs and it’s not in the 'default search' box, so I’ve no idea how it even got onto my pc.

Hi, sorry to hear you are having a problem; please try working through https://malwaretips.com/blogs/remove-safesear-ch/ by Malware Tips.

Note that not all removal programs will detect all malware, so you may need to run several or all of them.

You can also check your Firefox Desktop shortcut for corruption: Right click on it > Properties, and in Target, make sure there is no sign of the malware. If there is, delete that part of it. Or if it's easier, you can just delete and recreate a new shortcut.

Another thing you can do, is to search for the malware in your PC's search box.

After removal you may need to reset your home page and search, which you can do by running the add-on SearchReset.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you!