Are you using either Firefox for Android or Firefox for iOS on that Sync account? If so, that device may be the root of the corruption.

Disconnect each device from Sync.

Run Places Maintenance on each of the desktop / laptop devices. https://addons.mozilla.org/en-US/firefox/addon/places-maintenance/ That should fix the duplicates on each device.

Reset your Sync / Firefox Account Password (from the first device) to clear the corrupt data from the Sync server.

Then connect each of the desktop / laptop devices to Sync, going slow - one at a time, and make sure each device has correct data before proceeding to the next device.

One thing I might add here, please ignore if it has already been resolved. If this happens again, try to disable syncing addons in the Sync preferences to isolate if its an issue with syncing functionality there.

Otherwise I would be curious where the duplicates were (which folder) to file a proper bug.

Best!

I am running Windows OS and am able to access Options, Sync and disable sync. I can then go to Bookmarks, All Bookmarks and highlight all 5 lists of Bookmark listings, go to Organize and delete them.

That was my secondary computer. I can do the same thing on my Primary computer except I leave one list of Bookmarks not deleted. I then go to Sync and try and create a new account with a new password. Firefox will not let me create a new password with my old email address. When I try and use a new email address, Firefox tells me that and old email address and sync account is tied to that computer and I must login to my old email address and old password.

Then I login and turn on Sync and I get the 5 consecutive Bookmark lists back. Thbe problem is that the old list is in the Cloud and I can't modify it.

Sounds like corrupt data that is "stuck" on the server.

But you didn't answer me whether you're using a "mobile" device or not. If that is the case, I would suspect that "mobile" is at fault with that corruption of your bookmarks.

1. Disconnect all devices from Sync, using the 3-bar button and the "Menu panel".

2. Then load this page and Change your Password. https://accounts.firefox.com/settings or this one https://accounts.firefox.com/reset_password That will clear your data from the Sync server, allowing a fresh load from your devices.

3. Clean up your bookmarks, however you wish - but I do recommends using Places Maintenance to fix the Places database on all "desktop" devices.

4. Then reconnect each device to Sync and allow 15 minutes or so for complete synchronization for each device before connecting the next device.

The vast majority of questions I see about duplicated bookmarks involve use of Firefox Sync.