That is not really a Firefox question. Most Windows users would browse with Anti Virus software active. On Windows 10 you will normally have Windows Defender installed. However you may have opted to replace that with some paid for software. (Which unfortunately probably comes with unnecessary and problematic ''Free'' additional software) See also * [[How to stay safe on the web]] * How-To Geek: [http://www.howtogeek.com/howto/15788/how-to-uninstall-disable-and-remove-windows-defender.-also-how-turn-it-off/ How To Uninstall, Disable, and Remove Windows Defender] Unrelated but the forum software picks up that you apparently have two versions of Flash Player installed (Shockwave Flash) That could cause problems. You should have the latest version for Firefox, but not any earlier versions still installed. Adobe have an uninstall guide and utility * Adobe Flash Player > Uninstall Flash Player | Windows https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html