## Entity alias mapping

Previously, an entity in Vault could be mapped to multiple entity aliases on the same authentication backend. This
led to a potential security vulnerability (CVE-2021-43998), as ACL policies templated with alias information would match the first
alias created. Thus, tokens created from all aliases of the entity, will have access to the paths containing alias 
metadata of the first alias due to templated policies being incorrectly applied. As a result, the mapping behavior was updated 
such that an entity can only have one alias per authentication backend. This change exists in Vault 1.9.0+, 1.8.5+ and 1.7.6+.