The ShipStation.com plugin 1.1 and earlier for CS-Cart allows remote attackers to insert arbitrary information into the database (via action=shipnotify) because access to this endpoint is completely unchecked. The attacker must guess an order number.
https://www.jerdiggity.com/node/870
https://help.shipstation.com/hc/en-us/articles/360025855352-CS-Cart