How to stop Safari from leaking your data - use @DuckDuckGo
Prof. Douglas J. Leith tested six (6) major browsers and documented the results on a paper, “Web Browser Privacy: What Do Browsers Say When They Phone Home?”. Prof. Leith found out that Safari connects to remote servers, the search engine’s and Apple’s.
“This happens via the search autocomplete feature, which sends web addresses to backend servers in realtime as they are typed”
To protect you, change default search engine to @DuckDuckGo and then turn off all other options, including “Include search engine suggestions”, and if you don’t trust Apple, block api-glb-dub.smoot.apple.com.