Ever since the latest "Quantum" Firefox update, the Firefox main process has been hogging between 25-50% minimum CPU resources. I have a dual core 3.0 GHz processor in my PC, and Firefox is using 25% minimum of one core and nearly 50% of the other core. I tried turning off hardware acceleration and turning off accessibility permission (as some other support personnel have suggested to other users with similar issues), but both revert back to enabled when I restart Firefox. I do not have any extensions installed, and I don't have any themes installed either (I'm using the default). Also, I don't have any add-ons except for Flash, which is set to "Ask for activation." So, I'm running a very basic installation of Firefox, as I always have, but I've never experienced this CPU resource hogging behavior. One thing I should mention is that I do have a lot of tabs open, and I use three Firefox windows to display them in. One of my FF windows probably has at least 50 tabs. But this is nothing new. I've always had lots of tabs and several FF windows open at one time but never experienced this slowness before the latest upgrade. The only workaround is for me to shut down FF and use Chrome until I need to access one of the FF tabbed pages that I visit on a regular basis. This is very disappointing because I definitely prefer FF to Chrome, but I may be forced to ditch FF or only use it minimally if this problem persists. I also can't stop that stupid Bookmarks sidebar from automatically appearing and taking up screen space every time I start FF. I've looked for solutions and tried them, but none have worked so far.