Safari's Private Relay Leaks IP Addresses Through Passkey Authentication

The Privacy Gap in Apple's Shield

Apple's Private Relay feature promises to obscure your IP address from websites and even from Apple itself when browsing through Safari. The iCloud+ service routes your traffic through dual relays, separating identity from destination. But security researchers Talal Haj Bakry and Tommy Mysk have uncovered a fundamental flaw: the system fails when passkeys enter the authentication flow.

The vulnerability stems from how WebKit, Apple's browser engine, handles authentication requests outside the browser sandbox. When a user initiates a passkey login, the device generates an authentication request that bypasses Safari's privacy layer entirely. Private Relay operates within the browser context, not at the system level like a traditional VPN, creating an architectural blind spot that exposes the user's real IP address to the service they're logging into.

At DailyTechWire, we've tracked the growing adoption of passkeys across Asia-Pacific platforms, from Singapore's digital banking apps to Seoul's e-commerce giants. The technology promises to eliminate passwords through cryptographic key pairs stored on devices. But this WebKit issue reveals a tension between emerging authentication standards and privacy infrastructure that was designed for an earlier web architecture.

A Problem Bigger Than Safari

The implications extend beyond Apple's own browser. Because iOS mandates that all browsers use WebKit as their rendering engine, privacy-focused alternatives like OnionBrowser and Psylo inherit the same vulnerability. Users who choose these browsers specifically for anonymity, believing their Tor routing or other privacy measures protect them, remain exposed during passkey authentication.

Bakry and Mysk discovered the issue in late June after a user reported unexpected behavior in Psylo, their privacy-oriented browser. Their investigation revealed not just the passkey leak but additional DNS vulnerabilities in WebKit's handling of authentication flows. The researchers have shared their findings with OnionBrowser and the Tor Project, providing potential solutions.

This isn't an isolated incident in Apple's privacy tooling. The researchers point to a similar case involving iCloud's Hide My Email feature, where a separate research team identified a leak in mid-2025 that exposed real email addresses behind generated aliases. Apple took a full year to deploy a fix. The pattern suggests that privacy features, once shipped, may not receive the rapid iteration that security-critical vulnerabilities typically command.

The Architectural Trade-Off

The core issue lies in Apple's decision to scope Private Relay to the browser layer rather than implementing system-wide traffic routing. A VPN encrypts and routes all device traffic through an intermediary server, masking the origin IP for every network request. Private Relay, by contrast, activates only within Safari's web browsing context.

Passkey authentication operates at the operating system level, leveraging secure enclaves and biometric verification outside the browser's control. When Safari initiates a passkey flow, it hands off the authentication request to iOS system services. That handoff crosses the boundary of Private Relay's protection, leaving the IP address visible to the authentication endpoint.

For developers building services across Asia, where passkey adoption is accelerating faster than in Western markets, this creates a dilemma. The technology stack that promises the strongest authentication security undermines the privacy layer that many users expect from Apple's ecosystem. Companies processing authentication logs in jurisdictions with data localization requirements now have access to IP addresses that users believed were masked.

Response and Timeline

Apple confirmed to multiple outlets that it is investigating the researchers' report. The company has not provided a timeline for a fix or detailed whether the solution will involve changes to WebKit's authentication handling, adjustments to Private Relay's scope, or guidance to users about the limitations of the feature.

The researchers structured their disclosure carefully. After identifying the vulnerability in late June, they contacted affected browser developers and the Tor Project before making their findings public in early August. Their post on X outlined the responsible disclosure process and acknowledged the complexity of coordinating fixes across multiple stakeholders when the underlying issue sits in Apple's control.

The delay in addressing the earlier Hide My Email vulnerability suggests that users should not expect an immediate patch. Apple's privacy features often involve intricate coordination between iCloud services, operating system components, and third-party integrations. Rolling out a fix that doesn't break existing passkey implementations or introduce new edge cases will require extensive testing.

What This Means for Privacy-First Users

For individuals who rely on Private Relay as a lightweight privacy tool, the practical impact depends on their threat model. If the goal is to prevent casual tracking by advertising networks or to obscure location from content providers, Private Relay still offers value for standard browsing. But if the objective is anonymity from services you authenticate with, the feature provides a false sense of security.

Users concerned about IP exposure during passkey logins have limited options under iOS. Switching browsers won't help, given the WebKit mandate. Using a traditional VPN alongside Private Relay introduces complexity and potential routing conflicts. The most conservative approach is to avoid passkey authentication on sensitive accounts until Apple ships a fix, falling back to password managers or TOTP codes.

The broader question is whether Apple's incremental approach to privacy tools, layering features like Private Relay and Hide My Email onto existing architectures, can deliver on the company's privacy marketing without the deeper system redesigns that true anonymity requires. Each new authentication standard or web API introduces fresh surface area where privacy boundaries can fail.

The researchers' findings underscore a reality that Asia's tech community has long understood: privacy is not a feature you ship once, but a continuous alignment process between evolving protocols, user expectations, and the architectural decisions made years earlier. As passkeys become the default authentication method across the region's digital services, the gaps in Apple's privacy tooling will only grow more visible.