You can check for recently installed suspicious or unknown extensions.

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

You can check in "Windows Control Panel > Programs" for recently installed programs to see if any suspicious software shows up.

• Control Panel > Programs > Programs and Features > Uninstall or change a program
• click the Installed column to sort by this heading

You need to first provide complete information about the system your using for example windows or mac etc. After that may be better able to provide you with effective solutions. Also are you using the latest firefox version?

cor-el said

You can check for recently installed suspicious or unknown extensions. 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

You can check in "Windows Control Panel > Programs" for recently installed programs to see if any suspicious software shows up.

• Control Panel > Programs > Programs and Features > Uninstall or change a program
• click the Installed column to sort by this heading

Thanks but the problem continues.

I had two extensions -- Evernote and McAfee, both of which were disable, to no effect. I don't see any suspicious software in the control panel.

kathbaines said

You need to first provide complete information about the system your using for example windows or mac etc. After that may be better able to provide you with effective solutions. Also are you using the latest firefox version?

W10 pro with firefox 54.0 (32-bit).

Thanks.

HelpAsNeeded said

cor-el said

You can check for recently installed suspicious or unknown extensions. 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

You can check in "Windows Control Panel > Programs" for recently installed programs to see if any suspicious software shows up.

• Control Panel > Programs > Programs and Features > Uninstall or change a program
• click the Installed column to sort by this heading

Thanks but the problem continues.

I had two extensions -- Evernote and McAfee, both of which were disable, to no effect. I don't see any suspicious software in the control panel.

McAfee could be an issue. When you're on the Options page, Search panel, and you check the default search engine setting at the top of the page, does it switch to the search plugin with the McAfee "M on a shield" icon, or the Yahoo "Y in a box" icon?

After disabling McAfee, did you exit out of Firefox and restart it to make sure it was fully disabled? That may be necessary to prevent it from repeatedly taking over your search engine setting.

Evernote should not be a problem.

jscher2000 said

When you're on the Options page, Search panel, and you check the default search engine setting at the top of the page, does it switch to the search plugin with the McAfee "M on a shield" icon?

Yes, thanks!

Has disabled McAfee entirely on my laptop?

Disabling or removing a McAfee extension in Firefox does not disable other McAfee software on your system.