The application of open-source software in cybersecurity

I’m researching the use of open-source stack in the cybersecurity field and figured this would be an excellent place to ask.

I have a few questions to ask:

1. Do you use open source in your company, and what is your process for approving an open-source solution?
2. Does your company secure its SDLC (software development life cycle)?
3. What tools do you use to keep your SDLC secure?
4. In your opinion, what are the biggest pros and cons of using open-source tools in cybersecurity?

I'd really appreciate any help you can provide.