view_component: System Test Entry Point Path Check Allows Sibling Directory Escape

view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. From 3.0.0 to 4.9.0, the system test entrypoint canonicalizes a user-controlled file path with File.realpath, then checks whether the resolved path starts with the temp directory path. This is not a safe containment check because sibling directories can share the same string prefix. This vulnerability is fixed in 4.9.0.