When Jenkins is installed behind a reverse proxy, the hostname/port it uses internally may be different than what users see. The plugin should generate URLs relative to the 'Jenkins URL' set in the configuration page, rather than something detected internally.

For example, given http://build.example.com/jenkins, other plugins correctly show their urls as build.example.com/jenkins/plugin/... but the cluster stats plugin shows it at jenkins:8080/jenkins/plugin/..., which is the cluster-internal-only name/URL.