Apple’s iCloud Private Relay is designed to protect Safari users’ privacy by preventing any single third party from learning where requests originate or which sites you visit. However, new research suggests there are scenarios where a user’s real IP address can still become visible—because parts of the WebKit networking stack can route traffic outside the intended proxy path.
The findings, disclosed by researchers Talal Haj Bakry and Tommy Mysk, focus on how specific WebKit features behave on iOS, iPadOS, and macOS. The work indicates that the privacy guarantees of iCloud Private Relay may be weakened if the browser’s traffic can “escape” the relay route.
How iCloud Private Relay is supposed to work
iCloud Private Relay was introduced with iOS 15 and later made available as part of the iCloud+ subscription. The core idea is a dual-hop architecture: web traffic is routed through two relays so that no single external party can both identify the source and observe the destination.
In theory, this reduces the ability of intermediaries—aside from the relay system itself—to link a browsing session to a specific network location or target site.
Where the leak risk comes from: WebKit proxy bypasses
The researchers attribute the issue to three WebKit-related features that can bypass the configured proxy and send traffic directly from the device. Because the relay system relies on that proxy configuration to keep requests within the privacy-preserving route, bypassing it can reveal the device’s real network address.
They specifically point to these WebKit behaviors:
- DNS prefetching, which resolves hostnames through the device’s normal DNS route rather than the browser’s configured proxy path.
- WebAuthn related origin requests, which can cause the operating system’s credential service to fetch a validation file directly from the device.
- WebTransport, which can open a direct HTTP/3 connection that skips the proxy.
Importantly, the impact is not limited to Safari alone. Since WebKit is the default web rendering engine on iOS and iPadOS—and also powers other iOS browsers—the same underlying networking stack can affect browsers such as Google Chrome, Microsoft Edge, Mozilla Firefox, Brave, and others that rely on WebKit on Apple platforms.
Why these features matter for IP privacy
In all the scenarios described by the researchers, the device’s actual IP address may leave the intended relay path. That means a site could potentially observe the user’s real network identity even while iCloud Private Relay is enabled.
There’s also an additional nuance: not every browser setup is affected in the same way. The researchers note that the leak behavior depends on WebKit’s proxy configuration APIs and how different browser environments use them.
The WebAuthn angle: passkeys and real IP visibility
A key part of the report is how WebAuthn—the web standard behind passkeys—can be used to trigger the types of requests that may reveal an IP address.
The researchers explain that any website capable of integrating with the WebAuthn API could be configured in a way that makes WebKit reveal the browser’s real IP address, effectively bypassing both the proxy configuration and iCloud Private Relay in Safari.
According to Mysk, a website would need to intentionally take advantage of the bug to link a user’s current browsing session to the leaked IP address. They also state that this does not require user interaction or the use of passkeys.
Testing for possible leaks with a proof of concept
To help users validate whether they may be affected, a proof-of-concept website named leaks.psylo.app has been shared. The site is intended to check whether real IP information can leak out even when Private Relay is turned on.
The proof-of-concept separates regular connection behavior from the “possible” IP leak signals. The researchers use the term possible because not every browser is affected, and because there are mitigations such as using a VPN.
Mitigations mentioned by the researchers
The research points to VPN usage as one way to reduce exposure. Because a VPN can change the network path and apparent source address, it may make it harder for the browsing device’s real IP to be the one observed at the destination.
In their comments, the researchers also highlight that the behavior may vary by platform and browser implementation. For example, they note that desktop Chrome is not affected in the same way.
Does this affect other Apple OSes and WebKit browsers?
Yes. The report states that macOS is also affected, and that any WebKit-based browser that uses WebKit’s proxy configuration APIs can be impacted. This means the same core mechanism can apply across different Apple platforms and across third-party browsers—so long as they rely on the WebKit networking stack in the relevant way.
From a user perspective, this shifts the concern from “a single app” to a more general “engine-level” privacy risk.
What’s next and how Apple responded
Apple did not immediately respond to the researchers’ request for comment. However, the company told 404 Media that it is investigating the report.
This disclosure is also not the first privacy-related issue tied to iCloud Private Relay. Shortly after the feature launched in 2021, FingerprintJS highlighted a WebRTC-based mechanism that could leak a client’s real IP address.
Additionally, the report arrives a little over a month after Apple addressed a vulnerability in its Hide My Email service. That issue could unmask users’ real email addresses under certain conditions, reducing the effectiveness of the feature’s privacy promise.
Practical takeaways for users
If you rely on iCloud Private Relay for browsing privacy, it’s worth understanding that “privacy protection” can be complicated by how modern web features handle network requests behind the scenes. The researchers’ report suggests that some WebKit behaviors may route traffic outside the intended relay path in specific conditions.
As a practical step, users who want to confirm exposure can use the provided proof of concept and consider network-level mitigations like VPN usage. At the same time, it’s important to remember that the report emphasizes “possible” leaks—suggesting results can vary based on browser type, platform, and configuration.
Conclusion
The new research raises a serious but specific concern: iCloud Private Relay real IP visibility may be possible when WebKit features such as DNS prefetching, WebAuthn related origin requests, and WebTransport bypass the proxy route that iCloud Private Relay depends on. Because WebKit powers many browsers on Apple devices, the risk can extend beyond Safari itself.
For now, the best approach is to stay informed, test if you’re concerned, and use mitigations like VPNs until Apple addresses the underlying behavior through updates.
Source: https://thehackernews.com/2026/08/webkit-proxy-bypasses-can-expose-real.html
