To keep container builds updated to the latest parent (base) images projects typically use floating (rolling) image tags. But there is an issue with this approach - it leads to non-reproducible builds and makes it impossible to validate all the builds in a release that are based on the same parent image. Red Hat products require that builds be reproducible. To address this issue, CPaaS can use static image tags which are automatically updated when the floating tags change.
https://cpaas.pages.redhat.com/documentation/users/midstream/container_parent_image_updates.html