Please remove Shockwave Flash 11.2 r202 like this is a antique and a security risk. Current version is Flash Player : 27.0.0.187 as to how you uninstall in Linux I have no idea. Check in your installed programs for anything that should not be there. Something has hijacked your homepage I would guess. Very limited in what help there is for Linux. https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware. You will have to look for anti-malware programs that will run on your version. Please let us know if this solved your issue or if need further assistance.