We identify a set of challenges and opportunities for improving the security of software ecosystems and supply chain processes as software product components move through them. We focus attention to the role of explicit open architecture software ecosystem models spanning processes for software sourcing, integration, deployment, and evolution. These architectural models are relevant irrespective of the composition of organizational actors that delineate a software ecosystem. Consequently, every software ecosystem has one or more architectural models that can be visually mapped, communicated, and understood to improve supply chain process security.