Recent campaigns targeting npm, PyPI, and Docker Hub reveal a decisive shift: attackers now prioritize credential harvesting from developer endpoints over direct code tampering. Unlike traditional supply chain vectors focused on shared repositories or CI/CD platforms, these incidents exploit the concentrated context on workstations—local repos, .env files, SSH keys, and build scripts—that provide both initial access and a map to broader systems. This pattern, evident in TeamPCP and Shai-Hulud operations, turns ordinary laptops into high-value nodes capable of altering trusted software at scale. Mainstream coverage has overlooked how endpoint security gaps directly undermine supply chain governance, creating blind spots where a single compromised device can cascade into repository admin rights or package publication. Drawing from the SolarWinds compromise, where build-system access enabled widespread insertion, and the 2024 XZ Utils backdoor attempt that targeted maintainer environments, the evidence shows developer machines now concentrate delivery authority far beyond standard corporate data risks. Security teams must integrate workstation telemetry with identity and application controls, or face self-propagating attacks that exploit the trust developers inherently hold.