Open-source software is software which is released under a Copyright license which allows anyone the ability to inspect, modify, and distribute the code for any purpose. It is often developed in a public, collaborative manner.
There is a difference between open-source and “source available” software. Some software projects, such as GitLab Enterprise Edition, publish their source code for inspection, but do not allow people to freely use, modify, or distribute their source code. Source availability still provides the advantage of allowing users or security researchers to audit the code for vulnerabilities.
This is a common misconception, but whether the source code is available and how software is licensed does not inherently affect its security in any way. Open-source software has the potential to be more secure than proprietary software, but there is absolutely no guarantee this is the case.
Being open-source is a strong consideration when we review and recommend products, and we tend to prefer open-source software wherever possible. However, we do recommend proprietary software when it provides a significant privacy or security advantage that open-source alternatives may not yet provide.