Is this problem on your Windows 8.1 system?

You may need a little bit of persistence to clean this up. In case you haven't already, please:

(1) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it. Take out as much trash as possible here.

(2) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons
• in the Windows "Run" dialog, type or paste
  firefox.exe "about:addons"

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(3) You can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

Success?

Once you have removed all bad software and add-ons, the next step is to clean your Firefox shortcut. Either:

• right-click your Firefox desktop shortcut > Properties
• right-click your Firefox pinned Taskbar icon > right-click Mozilla Firefox > Properties

Windows should display the Shortcut tab with the Target highlighted. Make sure there is no extra address at the end, it should just be this (64-bit Windows):

"C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

Finally, if there are issues with Firefox's internal settings, here are some references:

(1) Home page

• Startup, home page, tabs, and download settings
• How to set the home page

(2) Default search engine

• Use the Search bar in Firefox and manage search engines

(3) New tab page

Here's how you can change your new tab page:

(A) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(B) In the search box above the list, type or paste newtab and pause while the list is filtered

(C) Double-click the browser.newtab.url preference and enter your preferred page:

• Page thumbnails (default) => about:newtab
• Blank tab => about:blank
• Built-in Firefox home page => about:home
• Any other page => full URL to the page

Press Ctrl+t to open a new tab and verify that it worked. Fixed?