Current Firefox releases have multi-process windows enabled. You may see three or more Firefox processes running.

• one process for the main Firefox thread (user interface)
• one or more processes for content threads set via "Options/Preferences -> General -> Performance" (dom.ipc.processCount)
• one process for the compositor thread (Windows)

You can look in "Help -> Troubleshooting Information" (about:support) to see the current multi-process state.

• "Help -> Troubleshooting Information" -> "Application Basics":
  Multiprocess Windows
  Web Content Processes

See also:

• https://www.ghacks.net/2016/07/22/multi-process-firefox/

Already know that. I'm not talking about the task manager here, what I'm talking about is the default apps list (Windows Settings -> Apps -> Default apps -> Set defaults by app).

Normally, freshly installed Firefox has just one item there, but if you click to set Firefox the default browser from inside the Firefox itself other than the Windows settings it creates another item named "Firefox" on that list.

Just to be clear, setting Firefox as the default browser from Windows settings doesn't have this problem.

In future please turn on send info to Mozilla before making a post. We have no info to help you with that would have been sent to help us understand Extensions, video card, Flash ......

Try fixing any issues in Windows 10

Please remove Firefox as default in every instance. Reboot. Then fallow below please.

Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Run the Windows Deployment Image Servicing and Management (DISM) and System File Checker (SFC) tools as Administrator. The DISM and SFC tools scan the integrity of the Windows image and all protected system files replaces corrupted, damaged and incorrect versions. (FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

Windows 10 To run the DISM command use the Windows key + X keyboard shortcut to open the Power User menu, then select Command Prompt (Admin). Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter. While running DISM you may notice the process will appear to pause at 20%. After a few minutes the operation will continue.

SFC fixes files locally using files on your system DISM goes up to Microsoft and gets new files.

Please let us know if this solved your issue or if need further assistance.

I didn't send any information because, first, I don't trust Mozilla/don't believe what they say about what they do with that information, second, this is not a local issue as you presume. As I said before, it happened on both of my computers, both having different hardware, freshly installed Firefox (not logged-in). So, instead of generic answers can someone with the latest Windows update just do what I did and tell if they were able to reproduce this issue or not.

Google Chrome had a similar issue like this reported by many users, which never been fixed. I hope Firefox devs really look into these issues unlike Google.

Sorry that is not the way things work. Follow suggestions or do what ever you want to. But not here. Or wait for a fix since you believe it is a FF problem and not local. So again do as you please.

Note : Firefox 57 Quantum release date is Nov 14th. https://www.mozilla.org/en-US/firefox/quantum/ Note: all Legacy Extensions will be disabled or removed.

Regards. Please let us know if this solved your issue or if need further assistance.

Either a Firefox or a Windows issue, either way just wanted to let the Firefox team know that there is one and it's affecting their beloved product.

By the way, there are no duplicates on the legacy control panel. The new menu came with Fall Creators Update may be the problem here, as I originally thought.

Here are the steps to reproduce this issue under the newest Windows update, reduced into a video: https://my.mixtape.moe/zxiqlz.mp4

Using a third party host because this site won't allow me upload mp4.