I'm not familiar with the Privacy/Security folder you mention.

If this a folder on the hard drive or something in Firefox? Can you give more detail about its usage and data it stored?

I notice that you tagged the question with Sync. Are you using Sync and all all devices you mention connected to the same account?

It is a 'folder', if you will, in Firefox's Preferences - shows your passwords/user names/credit-bank card info for auto fill, etc. As I mentioned - restoring from a recent Time Machine backup did not restore that info. This is in the OSX version of Firefox - not sure if it is the same in a Window's version. In looking back the mistake I seemed to have made is having the other two computers 'on' when I did the clean up. That Sync trashed the Firefox support file on those two units at the same time is the only explanation I can see is to why they went missing. What is puzzling is why the Time Machine restore did not work with regards to that specific section of Firefox's preferences.

Do you mean that the whole "Settings -> Privacy & Security" tab is empty or are only some parts missing ?

The actual Tab is there. Saved auto-fill and passwords info is what the Time Machine restore did not or would not re-populate.

Do you mean that the about:logins page is empty and doesn't have your passwords ? If this did propagate via Sync to the other connected devices then you would need an older copy of key4.db (encryption key) and logins.json and possibly logins-backup.json that still has those logins. You can search the Time Machine backup for these files.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile