OWASP Mutillidae II is a free, open source, deliberately vulnerable web-application providing a target for the web-security enthusiast. Mutillidae can be installed on Linux and Windows using a LAMP, WAMP, and XAMMP. It is pre-installed on SamuraiWTF and OWASP BWA. The existing version can be updated on these platforms. With dozens of vulnerabilities and hints to help the user; this is an easy-to-use web hacking environment designed for labs, security enthusiast, classrooms, CTF, and vulnerability assessment tool targets. Mutillidae has been used in graduate security courses, corporate web sec training courses, and as an “assess the assessor” target for vulnerability assessment software.