Registrations for the Events Calendar <= 3.2 - Authenticated (Contributor+) SQL Injection via 'standard' Parameter

The Registrations For The Events Calendar plugin for WordPress is vulnerable to SQL Injection via JSON keys in the 'standard' parameter handled by the rtec_records_edit AJAX action in versions up to and including 3.2. The handler decodes attacker-controlled JSON from $_POST['standard'] and uses the JSON array keys directly as column identifiers in the SET clause of an UPDATE statement built inside RTEC_Db_Admin::update_entry(). Only esc_sql() (mysqli_real_escape_string) is applied to the identifier; that function escapes quotes, backslashes, and a few control characters but does not escape spaces, equals signs, parentheses, or hyphens, so an attacker can break out of the identifier context and inject subqueries (terminated with a SQL comment). This makes it possible for authenticated attackers, with Contributor-level access and above who can edit the targeted event, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.