Apple's iCloud Private Relay can leak a user's real IP address to websites due to a flaw in WebKit [1, 2].
This vulnerability undermines a core privacy feature marketed to protect users from tracking by masking their digital identity. If a user's true IP address is exposed, websites and third-party trackers can potentially identify their approximate physical location, and link their browsing activity to a specific device.
Security researchers Talal Haj Bakry and Tommy Mysk discovered that the leak occurs specifically during passkey authentication requests [1, 2]. When a website requests a passkey, the authentication process bypasses the Private Relay system entirely through a loophole in WebKit [2, 3]. This allows the destination server to see the user's actual IP address rather than the masked address provided by Apple's relay servers [1, 4].
The issue affects users browsing the web with Safari on both iOS and macOS devices [1, 2]. While Private Relay is designed to prevent network providers and websites from seeing both who the user is and what they are visiting, this specific flaw creates a direct path for data leakage [3, 4].
Apple has not yet released a fix for the vulnerability [5]. The discovery highlights a gap between the advertised privacy protections of the iCloud+ subscription and the technical implementation of passkey handling within the browser engine [4, 5].
Users who rely on Private Relay for anonymity may find their privacy compromised whenever they interact with sites utilizing passkey authentication. Because the bypass happens at the system level within WebKit, there are currently no user-facing settings to prevent this specific leak [5].
“Apple's iCloud Private Relay can leak a user's real IP address to websites.”
This flaw represents a significant failure in 'privacy by design,' as a security feature—passkeys—is inadvertently disabling a privacy feature. For Apple, it creates a reputational risk regarding its iCloud+ marketing. For users, it demonstrates that no single privacy tool is absolute and that system-level integrations can create unforeseen vulnerabilities.
