'm experiencing the high CPU utilization when FireFox is running that has been reported in other posts. I believe the problem is the result of an interaction between multiple products. Here is my trouble shooting approach. I disabled Adobe Flash plugin. CPU utilization dropped from 70%+ CPU (60% of which was System CPU) back to < 10% CPU. I reenabled Adobe Flash and opened FireFox. CPU was again 70%+. I closed all tabs that had Flash content. After a few seconds CPU went back to <10%. I opened Facebook and CPU went to 50+% CPU, most of which was System. I opened www.wral.com and CPU increased to 70%+. As I open additional flash content pages the CPU continues to increase. Other events that may be associated with this problem were: 1. An upgrade to Adobe Flash which also resulted in periodic Flash crashes. 2. An unwanted installation of McAfee Security Scan that came with a scam virus message. Online research suggested running Malware Bytes. 3. Installation of Malware Bytes 4. Removal of McAfee Security Scan The CPU issue appeared sometime during this process but I can't associate with an exact event. My conclusion is that the problem may be due to an interaction of my Antivirus software with flash content appearing in FireFox. Running: Windows 8.1 Firefox 36.0 Adobe Flash 16 NPAPI Trial Copy of Malware Bytes 2.0.4.1028 McAfee is at latest release My next step will be to deactivate Malware Bytes. After that I will uninstall and reinstall Flash. Looking for any additional ideas and a sanity check on my conclusions and next steps.