Private Relay’s Blind Spot: Passkeys and Hidden IP Exposure
The iCloud Private Relay leak is a WebKit security vulnerability where specific browser features bypass Apple’s Safari-only proxy protection, exposing an iPhone user’s real IP address during passkey-related authentication flows even when iCloud Private Relay is enabled and expected to hide that information. This is not a theoretical edge case; it challenges the core promise that Private Relay keeps browsing activity and location metadata obscured. Apple designed the service as a privacy layer for paid iCloud+ subscribers, but it only protects traffic processed inside Safari’s browser stack. When WebKit decides to send some requests outside that stack, Private Relay is simply not in the path. If you have been treating Private Relay as a VPN replacement, this flaw should be a wake-up call: your browser may be quietly telling sites where you are.
How WebKit Features Bypass Private Relay During Passkey Sign-ins
The heart of the passkey authentication flaw is how WebAuthn requests are handled on iOS. When a site prompts you for a passkey—or even pretends to support one—the related sign-in request is fetched by Apple’s system-level credential service instead of Safari’s usual networking layer. Because iCloud Private Relay only wraps Safari traffic, that system request never goes through the Private Relay path, and the destination server sees your real IP address. Security researchers Talal Haj Bakry and Tommy Mysk showed that a webpage can trigger a WebAuthn Related Origin Request so that Apple’s credential service connects directly from the device, exposing the true IP with no visible warning to the user. This means a site can quietly collect location and identity clues while advertising a privacy-respecting, passwordless sign-in experience.
Beyond Passkeys: Three WebKit Features That Break Proxy Privacy
The iCloud Private Relay leak is not limited to WebAuthn. Bakry and Mysk identified three WebKit features that bypass application-level proxy settings: DNS prefetching, WebAuthn Related Origin Requests, and WebTransport. DNS prefetching, available since iOS 26, can expose the DNS servers you use, hinting at your network environment. WebTransport, enabled in iOS 26.4, opens direct HTTP/3 connections from the device that reveal its IP. Combined with WebAuthn, these behaviors undermine Proxy-based tools that depend on WebKit honoring their routes. Because every iOS browser is required to rely on WebKit, the exposure affects Safari and third-party browsers alike. Privacy-focused apps that use application-level proxies, such as Onion Browser, are also impacted, with real IP addresses leaking even when users believe they are inside hardened, anonymity-preserving contexts.
Who Is Affected and Why a VPN Still Matters
Anyone on iOS who relies on iCloud Private Relay or an app-level browser proxy is in the blast radius of this WebKit security vulnerability. That includes iCloud+ subscribers using Safari, people who installed alternative browsers that still sit on WebKit, and users of privacy-centric tools such as Onion Browser and Psylo. The behavior has been present since iOS 18 for WebAuthn-related requests, with newer leaks appearing as Apple added DNS prefetching and WebTransport features in later releases. This matters because many users treat Private Relay as a privacy blanket comparable to a VPN, but it is explicitly not a system-wide tunneling service. In contrast, traditional VPNs that encrypt traffic at the operating-system level remain unaffected by these application-level bypasses, since they wrap all outgoing connections regardless of which component initiates them.
Apple’s Response and What Privacy-Conscious Users Should Expect Next
Apple has acknowledged the iCloud Private Relay leak report and stated that it is investigating the WebKit flaws. After the researchers formally submitted their findings, Apple updated the issue’s status to indicate that it plans to address the problem, with a fix scheduled for fall 2026. That timeline leaves a long window in which passkey-related IP address exposure can continue for iPhone users who trust Private Relay or WebKit-based privacy browsers to conceal their location. Given that a previous issue in Apple’s Hide My Email feature had to be patched after it was shown to expose real email addresses, users should treat this new leak as a reminder that paid privacy tools are not infallible. Until Apple’s fix arrives, the only rational stance is skepticism: assume that any passkey sign-in on iOS can reveal more about you than the interface admits.
