When someone uses the ?Private Browsing? feature of Safari, because you don't want to leave traces of the visited site But that's not what is happening with the Apple browser.
A file that is used exclusively to store the favicons (that little icon that appears next to the URL you typed) is causing this whole problem. Located in ~ / Library / Safari /, in addition to storing such images, the WebpageIcons.db also identifies the URL linked to a given favicon, even the user visiting the page using the ?Private Browsing?.
Although the problem has existed since 2013 (PDF), the AppleInsider tested everything even in the latest beta version of OS X 10.10.3 and the problem is also there.
Of course, to have access to this information, a person must necessarily have direct contact with his computer. Still, it is still a fault of Safari. For now, there are only two alternatives for not making the websites you visit using ?Private Browsing? be recorded: 1. by throwing the WebpageIcons.db file in the Trash (forcing Safari to recreate it); or 2. going on Safari Clear Website History and Data, something you could do without even using the ?Private Browsing? mode.
It is worth noting that, according to INFO he said, this .db s extension can be interpreted by browsers for SQLite (a C language library that implements an embedded SQL database).