Did you have Firefox installed on this computer before, and then uninstalled it and reinstalled? Firefox may have used your old profile.

Or, when you installed Firefox, there is an import wizard that appears. You likely clicked next in that window, which then imports your data from whatever browser you are using already. Or if you set up a Firefox Sync account and set that up in the new Firefox install, it will bring your bookmarks over from another computer as well.

I did not have Firefox on this computer before. I had not done any browsing on any other browsers on this computer--this machine is brand new. I must have, unbeknownst to me, set up the "Sync Account"??? How did Firefox know it was me? I created an account with Mozilla/Firefox just now to post this question yet those bookmarks, etc were downloaded the other day. I'm asking because I'm wondering if their tracking data can tell me where that laptop is since someone stole it from my home! (I know it seems ignorant, but there's got to be a way...)

If your stolen laptop continues to Sync with Mozilla's servers, you might have access to information about some of the browsing activity on that laptop, such as browsing history, new bookmarks, and new saved passwords. However, I suspect that iCloud is a more powerful tracking tool than Firefox Sync.

For your security on your new PC, you probably should create a new Firefox profile. One way to do this with minimal transitional pain is the use the Reset feature. This duplicates certain key data from your active settings folder into a new one, bypassing some add-ons and custom settings.

More information in this article: Refresh Firefox - reset add-ons and settings.

Do not sync your new profile with your old Sync account.

To access your old profile for any purposes, such as to delete any saved passwords or see whether you get any new data, you can switch back and forth using Firefox's Profile Manager. This article describes how to start Firefox in the profile manager. I do not recommend removing anything until you are 110% certain that you will never need any of that profile's data in the future. Profile Manager - Create, remove or switch Firefox profiles.

First, Mozilla does not track your computer, and has no way of finding out where it is or what happened to it. IF you have a Firefox Sync Account, when you set it up on your new computer, that is how Firefox knew it was you, because you put the username and password in for Sync.

Tyler, I did NOT enter any account info for the Mozilla Firefox download this weekend. I got the account this morning to post this question. There has to be another way they knew it was me.

jscher2000, That's very helpful information. However, I created this Mozilla Firefox account in order to post my original question this morning. My old bookmarks appeared on Saturday. I have spoken to the iCloud/Mac geniuses, they don't have any way to track my laptop. But, I'm guessing they just don't have access to that information. As much data is collected at any given moment...they know!

When Firefox is first installed it will ask if you want to import bookmarks and some other data from other browsers which are installed on that computer - Safari in the case of Macs. More than likely that is how Firefox "knew" all your bookmarks, etc. That is a feature all browsers have when they are first installed.

I'm not sure any of you are really "listening" to me. I had NEVER USED THE COMPUTER BEFORE INSTALLING FIREFOX. The bookmarks are from the laptop that was stolen. Period. I DO NOT HAVE A FIREFOX account until i posted this question. Do any of you even work for Mozilla Firefox??

egeo9, the account you used to post this question is not a "Firefox account". It is a support forum account, and is only used for the Firefox support forums. Firefox Sync (How do I set up Sync on my computer? is a totally different account. If this is from your old computer, you either transferred the data, used icloud to restore the data to your new computer, or set sync up on your computer and your old one.