WPP confirmed on Monday it is in exclusive talks with Bain Capital to sell its majority stake in Kantar to the Boston-based private-equity firm, following "press speculation." The potential deal values the data, insights and consulting giant at $4 billion, according to WPP's statement that confirmed an earlier Bloomberg report. "Bain Capital's proposal is subject to negotiation," the statement read. "There is no certainty that these discussions will result in a transaction involving Kantar. Any further announcement will be made as appropriate." WPP declined to comment further. Kantar and Bain Capital did not immediately return requests for comment.