If people only knew how bad the stock Mozilla Firefox was...

Go to the [|||] menu -> More Tools -> Task Manager

You will see 'Add-ons Search Detection'... a hidden add-on that doesn't show in the add-on list. If you hover over it, and click the jump arrow at the far right, you get it's unlisted add-on page.

Add-ons Search Detection Requires Access to Private Windows This extension has access to your online activities while private browsing. Learn more

Version 2.0.0 Last Updated January 10, 2022

Required permissions for core functionality: Access your data for all websites

And see the hidden spy ad on, that tracks every search query you make, then the result you get, to send back to Mozilla and partners. You can only disable it per session, then Mozilla Firefox restarts it.

Ostensibly, this is a research project to detect malicious replacement of search result links, even when you have overtly opted out o fall research projects and have painfully tried your best to manually disable all the vast extensive telemetry spy-tracking...

I expect Google Chrome to be even worse.