GHSA-q4rm-m6xh-5pv7: Froxlor customer can create MySQL databases on disallowed servers via Mysqls.add API

The Mysqls.add API command (lib/Froxlor/Api/Commands/Mysqls.php) accepts a customer-controlled mysql_server parameter and only validates that the value is numeric and that the server index exists in userdata.inc.php. It never checks the value against the calling customer’s allowed_mysqlserver allowlist. A customer can therefore create a database, plus a MySQL user with a password they choose, on any MySQL server the operator has configured — including servers that were explicitly excluded from that customer (e.g. a separate cluster, premium-tier host, or another tenant pool). The same allowed_mysqlserver check is correctly enforced in MysqlServer::get() / MysqlServer::listing() and in the customer-facing UI (customer_mysql.php), confirming the omission is a bug, not by-design.