The Open Security Summit 2019 is focused on the collaboration between Developers and Application Security and organised with the support of the Open Web Application Security Project (OWASP): a worldwide not-for-profit charitable organization focused on improving the security of software. Using the same model as the previous OWASP Summits, it will be a 5-day high-energy experience, during which attendees get the chance to work and collaborate intensively. This is not a conference with uni-directional presentations. Every thoroughly prepared working session is geared towards a specific Application Security challenge and will be focused on actionable outcomes.