"We may share internet usage information with ad networks and other advertising partners for the purpose of cross-context behavioral advertising. We may also share this information with other trusted partners... These trusted partners may use this information to support and market partnership benefits (including by communicating with you), as well as for their internal business purposes such as analytics and product improvement. Any such partner uses will be governed by the partners' respective privacy policies."
Grubhub shares user data broadly with ad networks, trusted partners, affiliates, and subsidiaries for advertising, analytics, and the partners' own business purposes, governed only by those partners' own policies.