Open-source software is software whose source code is publicly available for anyone to use, inspect, modify, and redistribute under its license. In security work, that openness is a strength because defenders can audit code, spot weak dependencies, and share fixes across a large ecosystem. It also means one flaw can affect many products that reuse the same library or component.
In real attacks, adversaries often look for unpatched OSS vulnerabilities in popular packages, build tools, or infrastructure components, then exploit downstream systems that depend on them. In defense, teams use vulnerability triage, coordinated disclosure, and advisory formats such as CVEs or OSV records to turn findings into patches or temporary mitigations quickly. OSS security therefore depends not only on code quality, but also on how fast maintainers, researchers, and users can coordinate response before attackers take advantage of exposed software.