WebKit structured-clone UAF CVE-2023-28205

iOS fixed in 16.4.1. Your build is vulnerable if this crashes WebContent.

1. Tap Start. The page loops history.pushState with cyclic Map/Set graphs.
2. Expected when vulnerable: tab reloads, freezes, or Safari dismisses — heartbeat stops.
3. Confirmation: this page auto-reports liveness; the lab console shows the session going dark.

Start test Start public PoC variant I saw a crash