The HAL Browser which is included in Spring Data REST by default is seemingly unmaintained (and has at least one known security issue):
Known security issue: https://github.com/mikekelly/hal-browser/issues/99
Spring Data REST developers have begun to move away from the HAL Browser in favor of the HAL Explorer as noted in this comment from a Spring Data Rest developer and as evidenced by this ticket: https://jira.spring.io/browse/DATAREST-1386
Additionally, Spring Boot is looking at moving to the new HAL Explorer module by default: https://github.com/spring-io/start.spring.io/issues/184
However, we would need to port any custom code (including our custom Shibboleth login code) from the HAL Browser over to the HAL Explorer.