Source Defense is a client-side website security solution that protects against malicious activity originating from third-party vendors in the website supply chain. The platform addresses vulnerabilities introduced by integrated third-party JavaScript vendors that create unmanaged connections between vendor servers and client browsers. The solution uses real-time sandbox isolation technology to prevent Magecart and Formjacking attacks. It applies automated and dynamic rules and policies using machine learning and industry best practices to control the access and permissions of all third-party tools operating on websites. Source Defense is delivered as an agentless, SaaS-based solution that deploys by adding two lines of code to website page headers. The platform provides automatic and dynamic policy configuration without requiring manual intervention or administration. The implementation process involves adding Source Defense code to the website HTML and selecting permission groups for third-party vendors. This approach allows organizations to maintain the business value from website supply chain vendors while preventing malicious data extraction or website alteration.