Enable PCM measurement by a third-party on behalf of a publisher (i.e. iFrame or SFrame)

[ranton256]

Publishers predominantly use iFrames or SFrames from ad-tech companies to render ads on their websites. This enables publishers to rely on ad-tech partners to monetize pageviews so they can focus on on-site content for their users. Apple’s PCM doesn’t support ad serving via iFrame or SFrame. Instead PCM requires a publisher domain to trigger PCM protocols directly. PCM implementation relies on publishers to build additional safeguards to prevent injection attacks of unsafe ads, discouraging adoption of privacy safe measurement from trusted third-parties. We request and support an approach similar to the Google Privacy Sandbox which support privacy safe measurement by enabling the publisher domain to delegate requests to a designated third-party.