Hi gohanman, Firefox is rolling out a new feature to separate the user interface and tab content into separate processes. This may cause you to see more than one firefox.exe or a larger than normal plugin-container.exe. (I'm not sure why some users see one and other users see the other.) So probably that's the situation -- especially based on what happened when you killed the process -- rather than plugins running when they're disabled.

The performance impact of multi-process (e10s) can vary a lot between systems: many users find it faster, some find it slower, for many it's neutral. If your Firefox seems to be running fine despite the extra process, I suggest letting it run that way to see whether any problems develop. That's how we'll shake out the bugs!

If you think Firefox is not performing well or is using an unreasonable amount of resources now, you could evaluate whether e10s is causing this problem by turning it off as follows:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste autos and pause while the list is filtered

(3) Double-click the browser.tabs.remote.autostart.2 preference to switch the value from true to false

Note: the exact name of the preference may vary, but it will start with browser.tabs.remote.autostart

At your next Firefox startup, it should run in the traditional way. Any difference?

Thanks, that helps quite a bit. Disabling this "e10s" functionality reduces CPU usage by about 50% and memory usage by about 10 fold (i.e., 1,000%). As an end-user, I think it would be helpful if Firefox didn't have a process named "plugin-container.exe" that had nothing whatsoever to do with plugins. This is quite misleading in understanding what is causing abysmal performance.