The Download Monitor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Cross-Origin postMessage to Admin Editor in all versions up to, and including, 5.2.10 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the attacker to trick an authenticated Administrator into visiting an attacker-controlled page that targets an open Download edit screen, after which the payload is persisted unfiltered via the Administrator's unfiltered_html capability and later emitted verbatim to the frontend by the [download_data] shortcode's unescaped post_content render path.