Security researchers Tommy Mysk and Talal Haj Bakry report that Apple’s iCloud Private Relay, a paid Safari protection feature, can expose users’ real IP addresses to websites that use—or impersonate—passkeys.
iCloud Private Relay is included with paid iCloud+ plans and is designed to hide IP and DNS information when browsing with Safari. It is not a VPN and does not mask all device traffic. Passkeys rely on the WebAuthn standard and store a private key on the device rather than in the Safari browser; the system-level request sent during a WebAuthn ceremony is not routed through Private Relay and can therefore reveal the device’s IP address.
How iCloud Private Relay fails with WebAuthn passkeys
According to the researchers, WebKit hands WebAuthn ceremonies to the operating system’s credential service, which issues the HTTPS request directly from the device and is unaware of any proxy the host app configured. A page can set rpId to a host of its choosing, and the fetch can fire without user interaction when mediation is set to “conditional,” with no UI appearing. Because the fetch is issued by the OS credential service rather than by Safari, it never enters Private Relay’s proxied path and the destination server sees the device’s real IP address.
An attacker can therefore set up a website that uses WebAuthn to determine the protected IP address of a visitor. The researchers note there is no visible passkey prompt or other indication that an IP address has been accessed in the background.
The team also identified two additional WebKit behaviors that can reveal networking details: DNS prefetching (added in iOS 26) can expose a user’s real DNS servers, and WebTransport (added in iOS 26.4) can reveal an IP address.
The researchers built a website to let users test whether iCloud Private Relay is leaking their IP address. Because the issue stems from how WebKit handles these features, some third-party browsers that rely on WebKit are affected as well.
Apple said it is investigating the report. The researchers conclude that Apple will need to address the underlying WebKit behavior; in the meantime, users seeking broader protection can opt for a VPN.
