SQL injection vulnerability exists in the order_by parameter of the /customers/search endpoint in Alex Tselegidis EasyAppointments <= 1.5.1. The vulnerability arises from unsanitized user input passed to the order_by method of the CodeIgniter Query Builder, enabling attackers to perform time-based queries and schema enumeration. Under certain MySQL configurations, the flaw may lead to remote code execution by writing a PHP shell using INTO OUTFILE.