The Booking for Appointments and Events Calendar - Amelia plugin for WordPress is vulnerable to SQL Injection via the `sort` parameter in the payments listing endpoint in all versions up to, and including, 2.1.2. This is due to insufficient escaping on the user-supplied `sort` parameter and lack of sufficient preparation on the existing SQL query in `PaymentRepository.php`, where the sort field is interpolated directly into an ORDER BY clause without sanitization or whitelist validation. PDO prepared statements do not protect ORDER BY column names. GET requests also skip Amelia's nonce validation entirely. This makes it possible for authenticated attackers, with Manager-level (`wpamelia-manager`) access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database via time-based blind SQL injection.

CWE-89 SQL Injection