The researchers argue that cookie syncing "can greatly amplify privacy breaches" since companies could merge their databases containing the browsing histories of users they're monitoring. Such sharing would be hidden from public view.
Those companies are then in "position to merge their database entries corresponding to a particular user, thereby reconstructing a larger fraction of the user's browsing patterns."
"All of this argues that greater oversight over online tracking is becoming ever more necessary," they wrote.
The paper was authored by Gunes Acar, Christian Eubank, Steven Englehardt, Marc Juarez, Arvind Narayanan and Claudia Diaz.
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