Yachtcontrol Webapplication 1.0 makes it possible to perform direct operating system commands as an unauthenticated user via the "/pages/systemcall.php?command={COMMAND}" page and parameter, where {COMMAND} will be executed and returning the results to the client. Affects Yachtcontrol webservers disclosed via Dutch GPRS/4G mobile IP-ranges. IP addresses vary due to DHCP client leasing of telco's.