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

Separate Issue; Your System Details shows; Installed Plug-ins Adobe PDF Plug-In For Firefox and Netscape 15.16.20045 Adobe PDF Plug-In For Firefox and Netscape 11.0.10 <br>Having more than one version of a program may cause issues. You must remove the older programs. Then get the current full installer. Adobe PDF Plug-In For Firefox and Netscape: '''[http://get.adobe.com/reader/ Adobe Reader Version 2015.016.20039]''' '''Note: Other Software''' is offered in the download. --------------- Security Issue: Update your Flash Player '''Note: Windows users''' should download the '''active_x''' for ''Internet Explorer.'' '''and''' the '''plugin''' for ''Plugin-based browsers'' (like Firefox). '''Note: Windows 8 and Windows 10''' have built-in flash players and Adobe will cause a conflict. Install the '''plugin only.''' Not the '''active_x.''' Flash Player '''Version: 22.0.0.192''' Flash Player (Linux) '''Version 11.2.202.626''' https://get.adobe.com/flashplayer/ Direct link scans current system and browser '''Note: Other software''' is offered in the download. https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) '''Note: Other software''' is offered in the download. ------------------- See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration