The RSS Aggregator – RSS Import, News Feeds, Feed to Post, and Autoblogging plugin for WordPress is vulnerable to DOM-Based Cross-Site Scripting via postMessage in all versions up to, and including, 5.0.11. This is due to the plugin's admin-shell.js registering a global message event listener without origin validation (missing event.origin check) and directly passing user-controlled URLs to window.open() without URL scheme validation. This makes it possible for unauthenticated attackers to execute arbitrary JavaScript in the context of an authenticated administrator's session by tricking them into visiting a malicious website that sends crafted postMessage payloads to the plugin's admin page.