view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 4.0.0 until 4.12.0, ViewComponent::Base instances retain render-scoped objects across calls to render_in; if the same component, collection, or spacer component instance is reused across requests, users, tenants, or threads, later renders can use stale helpers, controller, request, view_flow, format/variant details, and slot child context from an earlier render. This can cause authorization-aware components to render privileged UI for a lower-privileged user, generate links using a stale Host header, leak slot/helper state, and mix request context under concurrent rendering. This issue is fixed in version 4.12.0.