X0306 4 2015-12-23 0 0001158172 COMSCORE, INC. SCOR 0000806968 WPP plc 27 FARM STREET LONDON X0 W1J 5RJ UNITED KINGDOM 0 0 1 0 0001636586 Cavendish Square Holding B.V. LANN OP ZUID 167 3072 DB ROTTERDAM P7 NETHERLANDS 0 0 1 0 Common Stock 2015-12-23 4 P 0 30606 40.525 A 6312497 I See footnote Common Stock 2015-12-24 4 P 0 23600 41.3417 A 6336097 I See footnote The price reported in column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $40.05 to $40.75, inclusive. The reporting persons undertake to provide to the SEC, comScore, Inc., or any securityholder of comScore, Inc., upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (1) and (3) to this Form 4. These shares are owned directly by Cavendish Square Holding B.V., which is a wholly-owned subsidiary of WPP plc that WPP plc owns indirectly through a series of intervening holding companies. WPP plc is an indirect beneficial owner of the reported securities. The price reported in column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $40.95 to $41.38, inclusive. WPP plc, By: /s/ Paul Richardson, Global Finance Director 2015-12-28 Cavendish Square Holding B.V., By: /s/ A. van Heulen-Mulder, Managing Director 2015-12-28