# Exploit Title: WordPress Ultimate Member Plugin 2.0.38 CSRF
# Discovery Date: 03 / 05 / 2019
# Discovered By: Georg Knabl
# Vendor Website: https://ultimatemember.com/
# Software Link: https://wordpress.org/plugins/ultimate-member/
# Software Download URL : https://downloads.wordpress.org/plugin/ultimate-member.2.0.38.zip
# Version: 2.0.38 (probably also 2.0.39 and older versions)
# Fixed in Version: 2.0.40
# CVE: CVE-2019-10673
# Category : WebApps
# CWEs: CWE-352
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Vulnerability Description:
A CSRF vulnerability in a logged-in user's profile edit form in
the Ultimate Member plugin 2.0.38 for WordPress allows attackers to become admin and
subsequently extract sensitive information and execute arbitrary code. This occurs because
the attacker can change the e-mail address in
the administrator profile, and then the attacker is able to reset
the administrator password using the WordPress "password forget" form.
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Software Description:
The Ultimate Member plugin allows WordPress site owners to quickly implement a
membership area. In this area, VIP users can view content that is hidden to other
users. Additionally, the plugin provides functionality to edit the current logged-in
member's profile information. At the time of discovery, the Ultimate Member plugin
had more than 100.000 active installations.
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Attack Vector:
On the plugin page that allows members to edit their personal information, sensitive
details such as the e-mail address can be changed by the logged-in user. The users
managed by the plugin correspond to native WordPress users. Unfortunately, the
plugin fails to secure against Cross Site Request Forgery (CSRF) attacks. This
allows an attacker to prepare exploit code on another website and lure a logged-in
administrator of the target website that uses the Ultimate Member plugin to this
website. The website, then, sends a hidden POST request via a html form to the
vulnerable website that causes the plugin to change the e-mail address of logged-in
user to the e-mail address of the attacker. Now that the attacker's e-mail address
is associated with an administrator role, the attacker is able to reset the password
of the account using WordPress' "password forget" form. Subsequently the attacker
is able to log-in with administrator access and cause further damage such as:
* extract sensitive information (sensitive information disclosure)
* upload and activate plugins or themes (arbitrary code execution)
* edit files on the server using the built-in WordPress file editor (arbitrary
code execution)
* generate new admin user (backdoor)
The administrator is not informed about this attack but might have problems logging
in again as the password has changed. Even though the plugin sends a notification
e-mail stating the profile data has changed, this message is sent to the new e-mail
address, which now belongs to the attacker.
Recon:
An attacker may easily find out the presence of this plugin as it uses typical CSS
class prefixes in the frontend. The target URL of the CSRF form can be guessed as
it uses a default path. Alternatively, the attacker could request member access to
determine the actual URL. The admin's username has to be known but could either
be guessed or enumerated via WordPress' author pages assuming user ID equals to "1".
Enumeration example call: https://vulnerable-website.example.com/?author=1
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Exploit Code: (as placed on the third-party website that executes the CSRF. Tested
on Google Chrome 73.)
...arbitrary content...