WebKit Proxy/Private Relay Leak Test Suite

Based on Mysk Blog, 2026-08-04: IP and DNS Leaks in WebKit Affecting Proxy Browsers and Apple iCloud Private Relay. Reference PoC: leaks.psylo.app

1. DNS resolution leak

Click below to force a real network request to a unique per-visit hostname under d.leaktest.cgt.io, then check whether our authoritative DNS server saw the query.

2. WebAuthn Related Origin Requests leak

This test targets a different origin's rpId (randomly rp.leaktest.cgt.io or wt.leaktest.cgt.io) from this page's own origin — that cross-origin mismatch is what forces the OS credential service to fetch that host's /.well-known/webauthn directly. The check runs silently: it uses conditional mediation (mediation: "conditional"), so no system passkey/security-key prompt is shown — but the OS-level ROR fetch still happens in the background.

3. WebTransport leak

Opens a direct QUIC connection to wt.leaktest.cgt.io:4433.