They have added a new option to Firefox privacy settings, enabled by default of course, to allow "suggestions from sponsors" to "occasional"ly appear in the navigation bar dropdown, as if they were bookmarks. I noticed this by seeing a link to Office Depot in the pulldown, wondering what Office Depot page I had bookmarked or in my history, and discovering that it was an in-browser "sponsored suggestion". It appears to work by sending all your navigation bar typeahead to Mozilla so it can match you with a sponsor (oops about that privacy, lol). I'm not sure how recent this "feature" is, but I think it is recent, and I only noticed it today (I'm on LTS Firefox but installed an update a few days ago). Maybe the less stable releases have had it for longer.
Turning the sponsored suggestions off is not that difficult (see the url above for instructions), but Mozilla's unceasing obsession with inveigling advertising into the browser is... disturbing. Another day in the enshittification of the web.