Wp Rss Aggregator Cross-site Scripting

The WP RSS Aggregator WordPress plugin before 4.20 does not sanitise and escape the id parameter in the wprss_fetch_items_row_action AJAX action before outputting it back in the response, leading to a Reflected Cross-Site Scripting (2022-02-28, CVE-2022-0189)

The WP RSS Aggregator WordPress plugin before 4.19.2 does not properly sanitise and escape the URL to Blacklist field, allowing malicious HTML to be inserted by high privilege users even when the unfiltered_html capability is disallowed, which could lead to Cross-Site Scripting issues. (2021-11-29, CVE-2021-24768)

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>