Are you saying Firefox shares data to Alphabet beyond Google as the default search engine? If so and if it applies to Sync (as if the question from OP here) can you please share sources for that?
You stated:
Mozilla does, sharing your account data
You also provided evidence that Mozilla uses Google Analytics trackers on the Firefox’s product information website. I mentioned that it’s not sufficient evidence of your claim as the trackers are independent of Firefox the browser and Sync. Additionally, the use of trackers for websites is clearly identified on Mozilla’s Privacy Policies and there is not much else mentioned on the Privacy Policies outside of those trackers and Google’s geolocation services in Firefox.
You’ve also mentioned Google’s contract with Mozilla, which is controversial for many people, but isn’t evidence of Mozilla providing user data to Google even in conjunction with the previously mentioned trackers. You then discussed various other browsers, but I’m not sure how that is relevant to your initial claim.
While it seems we can both agree that Mozilla and it’s products are far from perfect, it is looking like your initial claim was baseless as you have yet to provide any evidence of your initial claim. Do you have any evidence through things like code reviews or packet inspections of Firefox or Sync that hints Mozilla is sharing additional information to Google? At this point, I would even accept a user(s) providing evidence of some weird behavior like the recent issue where google.com wouldn’t load in Firefox on Android if someone could find a way to connect the weird behavior to Mozilla sharing data with Google.
The analytics trackers that you mentioned would fall under Mozilla’s Websites Privacy Policy, which does state that it uses Google Analytics and can be easily verified a number of ways such as the services you previously listed.
However, Firefox sync uses accounts.firefox.com which has its own Privacy Policy. There is some confusion around “Firefox Accounts” as it was rebranded to “Mozilla Accounts”, which again has its own Privacy Policy. There is no indication that data covered by those policies are shared with Google. If Google Analytics trackers on Mozilla’s website are still a concern for these services, you can verify that the Firefox Accounts and Mozilla Accounts URLs do not contain any Google Analytics trackers.
Firefox has a Privacy Policy as well. Firefox’s Privacy Policy has sections for both Mozilla Accounts and Sync. Neither of which indicate that data is shared with Google. Additionally, the data stored via the Sync service is encrypted. However, there is some telemetry data that Mozilla collects regarding Sync and more information about it can be found on Mozilla’s documentation about telemetry for Sync.
The only thing that I could find about Firefox, Sync, or Firefox Accounts/Mozilla Accounts sharing data with Google was for location services within Firefox. While it would be nice for Firefox not to use Google’s geolocation services, it is a reasonable concession and can be disabled.
Mozilla is most definitely not a perfect company, even when it comes to privacy. Even Firefox has been caught with some privacy issues relatively recently with the unique installation ID.
Again, I’m not saying that Mozilla is doing nothing wrong. I am saying that your “evidence” that Mozilla is sharing Firefox, Sync, or Firefox Accounts/Mozilla Accounts data with Google because of Google Analytics trackers on some of Mozilla’s websites is coincidental at best. Without additional evidence, it is misleading or flat out wrong.
I’m not disputing the results, but this appears to be checking calls made by Firefox’s website (www.mozilla.org/en-US/Firefox/) and not Firefox, the web browser application. Just because an application’s website uses Google Analytics does not mean that the application shares user data with Google.