WPP CEO Cindy Rose said on the investor call after third-quarter results that Safari's block on identity resolution services has almost no effect on the holding's data-driven decisions. Apple described the block in a WebKit blog post on October 19.
Arete Research analyst Richard Kramer asked about the vulnerability. Rose said the holding does not rely on identity resolution alone: “it doesn't really impact our data solution at all.” She named the InfoSum platform as the main pillar, saying it is fully integrated into WPP Open. According to her, the platform combines consumer data, WPP's own data and signals from nearly 400 partners.
Apple describes the method itself this way. Third-party companies collect the email a user enters when logging in or subscribing to a newsletter. They send it to their servers, attach a persistent ID to it and return that ID to the page. In iOS, iPadOS, macOS and visionOS 27, Safari and WebKit block network access to such infrastructure. The block works at the domain level, so changing the structure of a request does not get around it.
Apple explains the decision by saying that even with data from a single company, a central service sees the same email across different sites and devices. For that service, this creates matching and targeting capabilities that an individual site does not have. The post does not name any companies, including ad platforms.
Rose noted that InfoSum also uses consumer identifiers as one of its sources. Her argument is that matching happens on the parties' own data, not through code on the publisher's page.
It is worth watching which domains Apple adds to the block after version 27 of its systems is released, and how identity market players respond.
