Have you tried to uninstall any suspicious/potentially unwanted program from your system control panel ? [http://windows.microsoft.com/en-in/windows-8/uninstall-change-program Uninstall/Change Program] and also from Add-ons section ? Goto menu>Add-ons>Extension>Remove any suspicious browser plugin. Also Have you run Some Malware scanner like these : [http://www.surfright.nl/en/hitmanpro Hitman] [https://toolslib.net/downloads/viewdownload/1-adwcleaner/ Adw Cleaner] [https://www.malwarebytes.org/ Malwarebytes] If you missed any of these steps then please go through them and after that do a clean scan from any one malware scanner.

Hi, also see [http://malwaretips.com/blogs/mystartsearch-removal/ Remove Mystartsearch virus (Easy Removal Guide)] by Malware Tips. '''Note that not all removal programs will detect all malware, so you may need to run several or all of them.''' ''If your question is resolved by this or another answer, please take a minute to let us know. Thank you.''

You can open the <b>about:config</b> page via the location/address bar and search for prefs that refer to <b>Mystartsearch</b>. You can reset user set (bold) prefs via the right-click context menu to the default value. *http://kb.mozillazine.org/about:config More links: *http://malwaretips.com/blogs/?s=MyStartSearch ----Do a malware check with several malware scanning programs on the Windows computer. *https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware 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:<br>http://www.malwarebytes.org/mbam.php *AdwCleaner:<br>http://www.bleepingcomputer.com/download/adwcleaner/<br>http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml *SuperAntispyware:<br>http://www.superantispyware.com/ *Microsoft Safety Scanner:<br>http://www.microsoft.com/security/scanner/en-us/default.aspx *Windows Defender:<br>http://windows.microsoft.com/en-us/windows/using-defender *Spybot Search & Destroy:<br>http://www.safer-networking.org/en/index.html *Kasperky Free Security Scan:<br>http://www.kaspersky.com/security-scan You can also do a check for a rootkit infection with TDSSKiller. *Anti-rootkit utility TDSSKiller:<br>http://support.kaspersky.com/5350?el=88446 See also: *"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked