"Advertising, Analytics and Business Partners (Limited to Non-Personally Identifiable Information). We may share aggregated or pseudonymous information (including demographic information) with partners, such as publishers, advertisers, measurement analytics, apps, or other companies. For example, we may tell an advertiser how its ads performed or report how many people installed an app after seeing a promotion."
Yahoo shares user data with advertising and analytics partners for targeted advertising purposes. While they claim it's limited to non-personally identifiable information, the broad sharing of pseudonymous and demographic data with advertisers, publishers, and measurement companies enables cross-context advertising.