I notice that although we have many tools for security tests (SAST, SCA), I couldn't find an open source project on github that implements those tests. I've searched for google, Mozilla, OWASP and other big companies repositories, some of them use dependabot but no one implements security tests in the CI/CD (Pull request flow).
I don't think these companies don't implement any type of security tests in their internal code repositories. So, is there any reason they don't do the same with open source projects? Why?
I thought that testing the code in the ci/cd flow was a good security practice, so what are the best practices in security for open source projects?