Does this happen at startup, new tab, or randomly during browsing? Can you spot any pattern to it?

Next time it happens, could you copy/paste the address of the page you land on into a reply? Sometimes the address contains parameters that help identify the source of the problem.

See:

• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

It only involves one site so far.

Redirected to: http://tracki112.com/search/click.php?cid=q179G777i615U336G329Y865&r=2&fw=50&fh=10&pw=-3&ph=-3&sw=911&sh=512&if=1&fp=1

Hmm, I just get a page saying an ID isn't found. Maybe this was part of some kind of click fraud scheme?

The tracki112.com is a malware that stores into the mozilla files. I had this problem too, what I did is to save my favourites , then I unilstalled mozilla , the first time i did I followed the instructions from a link found here, uninstall then delete mozilla files in the windows system. In my case the first try didn't work Reinstalled mozilla and had the same problem

So I discovered that in my hard drive there is a folder named Windows OLD. Just in case a restauration of the system is needed you don't lose your files and info.

This folder Windows Old has also mozilla files stored, here it was where the spyware was stored.

When I uninstalled mozilla the second time, i ereased the mozilla files from the windows normal system folder, and from the windows old folder, and reinstalled mozilla.

It worked and this bug is not present anymore.

I hope it helps