The Newsletters plugin for WordPress is vulnerable to time-based SQL Injection via the 'id' parameter in all versions up to, and including, 4.18.1 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with subscriber-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. An attacker can obtain the required nonce and subscriberauth cookie without a WordPress account by simply subscribing through the public newsletter form and opening the management link sent via email; the ownership check verifies only the subscriber_id field and does not validate that the injected id parameter belongs to the authenticated subscriber.
Attack Parameters
Impact Assessment
CVSS Vector v3.1