Did you get your Firefox from Mozilla.org ?

You may have ad / mal-ware. Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

• 1 Download Firefox Full Installer For All languages And Systemsv40 {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

These can't get your data back, but will help in the future.

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

Usually the Refresh feature doesn't run by itself, but you may see a button suggesting that you can speed up Firefox by restoring some default settings, and if you click it, that will trigger the Refresh feature.

If your clean Firefox gets reinfected after a Refresh, external malware is the most likely explanation, and if the tools in the above-linked article don't clear it up, I have two other suggestions:

(1) Manually clean up add-ons as follows:

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. Bear in mind that all extensions are optional, none come with Firefox, and you can learn more about them by checking their reviews on the Add-ons site.

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.

(2) Try the forums in the malware support article for assistance using advanced cleanup tools.