The Open Source Security Foundation (OpenSSF) has developed free courses for software developers on how to develop secure software.
The “Developing Secure Software” (LFD121) course is available on the Linux Foundation Training & Certification platform. It focuses on the fundamentals of developing secure software. Both the course and certificate of completion are free. It is entirely online, takes about 14-18 hours to complete, and you can go at your own pace. Those who complete the course and pass the final exam will earn a certificate of completion valid for two years.
If you prefer, the same lesson content is available on edX as part of the Secure Software Development Fundamentals Professional Certificate program. You can audit the course (to learn the material) for free. If you want to try to earn a certificate of completion on edX (to prove that you learned the material), there’s a fee. On edX the content is split into 3 courses: Secure Software Development: Requirements, Design, and Reuse (LFD104x); Secure Software Development: Implementation (LFD105x); and Secure Software Development: Verification and More Specialized Topics (LFD106x).
To propose changes to the course content and/or reuse the material,
see the course content repository on GitHub.