Patreon Wordpress Cross-site Scripting

The Patreon WordPress plugin before 1.8.2 does not sanitise and escape the field "Custom Patreon Page name", which could allow high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (2022-03-14, CVE-2021-25026)

The Jetpack Scan team identified a Reflected Cross-Site Scripting in the Login Form of the Patreon WordPress plugin before 1.7.2. The WordPress login form (wp-login.php) is hooked by the plugin and offers to allow users to authenticate on the site using their Patreon account. Unfortunately, some of the error logging logic behind the scene allowed user-controlled input to be reflected on the login page, unsanitized. (2021-04-12, CVE-2021-24228)

The Jetpack Scan team identified a Reflected Cross-Site Scripting via the patreon_save_attachment_patreon_level AJAX action of the Patreon WordPress plugin before 1.7.2. This AJAX hook is used to update the pledge level required by Patreon subscribers to access a given attachment. This action is accessible for user accounts with the ‘manage_options’ privilege (i.e.., only administrators). Unfortunately, one of the parameters used in this AJAX endpoint is not sanitized before being printed back to the user, so the risk it represents is the same as the previous XSS vulnerability. (2021-04-12, CVE-2021-24229)

Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.

The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:

https://server.com/confirmation?message=Transaction+Complete

what results in:

<span>Confirmation: Transaction Complete</span>

In that case the message can be modified to become a valid Javascript code, e.g.:

https://server.com/confirmation?message=<script>dangerous javascript code here</script>

and it will be executed locally by the user's browser with full access to the user's personal application/browser data:

<span>Confirmation: <script>dangerous javascript code here</script></span>