A fired executive at WPP is suing the advertising agency giant, accusing the company of retaliating against him and firing him after he raised concerns that the group's media investment division was allegedly running an improper kickback operation. Richard Foster spent 17 years working for GroupM, WPP's media arm, which controls more than $60 billion in advertising spending for clients such as Google, Unilever, and Ford. GroupM rebranded to become WPP Media this year.Foster was formerly the global chief ex ...