Many businesses, organizations, and social institutions use websites to support their main tasks. The various benefits of the website must be supported by the security aspects of the website in order to avoid hacking. Cyber attacks or hackers can do dangerous things like get more valuable data. So it is necessary to test a good website to find out the level of vulnerability of application features in it. A suitable test for websites where the website is distributed over a network is the grey box penetration test. This study performs a grey box penetration testing technique using the OWASP method and the OWASP ZAP tool. The test steps are collecting test target information, performing automatic scanning with the help of OWASP ZAP, exploiting the scan results, reporting, and providing recommendations. The test results show the target application website has 12 vulnerabilities with 8.3% at the high level vulnerability or 1 alert, 41.7% at the medium level or 5 alerts, 33.3% at the low level or 4 alerts, and 16.7 at the informational level or 2 alerts. These vulnerabilities are related to matters related to A01-Broken Access Control, A03-Injection, A05-Security Misconfiguration, and A08-Software and Data Integrity Failures.