This document provides an overview of secure coding with open source software. It discusses that open source software is now mainstream, used in many modern innovations. It describes what open source software is, the explosive growth of open source, and popular open source libraries and dependencies. The document outlines roles in open source projects and how to contribute. It discusses security considerations like vulnerabilities in open source libraries and the increased risk with reusing libraries. The document provides examples of popular open source projects like Angular.js and their contributions and vulnerabilities. It emphasizes the real risk is not a lack of fixes but the lack of speed in applying fixes. The importance of software composition analysis and vulnerability management for open source is highlighted.