Wordpress Plugin WP-UserOnline 2.88.0 - Stored Cross Site Scripting (XSS)

# Exploit Title: Wordpress Plugin WP-UserOnline 2.88.0 - Stored Cross Site Scripting (XSS)
# Google Dork: inurl:/wp-content/plugins/wp-useronline/
# Date: 2022-08-24
# Exploit Author: UnD3sc0n0c1d0
# Vendor Homepage: https://github.com/lesterchan/wp-useronline
# Software Link: https://downloads.wordpress.org/plugin/wp-useronline.2.88.0.zip
# Category: Web Application
# Version: 2.88.0
# Tested on: Debian / WordPress 6.0.1
# CVE : CVE-2022-2941
# Reference: https://github.com/lesterchan/wp-useronline/commit/59c76b20e4e27489f93dee4ef1254d6204e08b3c

# 1. Technical Description:
The WP-UserOnline plugin for WordPress has multiple Stored Cross-Site Scripting vulnerabilities in versions 
up to, and including 2.88.0. This is due to the fact that all fields in the “Naming Conventions” section do 
not properly sanitize user input, nor escape it on output. This makes it possible for authenticated attackers, 
with administrative privileges, to inject JavaScript code into the setting that will execute whenever a user 
accesses the injected page.
  
# 2. Proof of Concept (PoC):
  a. Install and activate version 2.88.0 of the plugin.
  b. Go to the plugin options panel (http://[TARGET]/wp-admin/options-general.php?page=useronline-settings).
  c. Identify the "Naming Conventions" section and type your payload in any of the existing fields. You can use 
 	 the following payload:
		<script>alert(/XSS/)</script>
  d. Save the changes and now go to the Dashboard/WP-UserOnline option. As soon as you click here, your payload 
  	 will be executed.

Note: This change will be permanent until you modify the edited fields.