FORBIDDEN ACT:indices:data/read/field_caps

yep I confirm the

prompt_for_basic_auth : true

then here , for peeps having this setting enabled and having trouble with xpack :

on top of rules, but below kibana server one, add rule for xpack monitoring user credential :

    - name: "x-pack monitoring"
      auth_key_sha1: 6fce414848684684de68d4ed68e4d47
      type: allow
      actions: ["cluster:monitor/*", "indices:data/read/*","indices:data/write/*","indices:admin/template/*","indices:admin/create", "cluster:admin/ingest/pipeline/*"]
      indices: ["<no-index>", ".monitoring-*"]
      verbosity: info

and last rules :

    - name: "just that action from localhost"
      type: allow
      actions: ["cluster:monitor/*", "cluster:admin/xpack/monitoring/*", "cluster:admin/xpack/license/*", "indices:data/read/*","indices:data/write/*", "indices:admin/create" ]
      hosts: ["127.0.0.1"]
      indices: [".monitoring-*"]
      verbosity: info
 
    - name: "field_caps stuff"
      type: allow
      actions: ["indices:data/read/field_caps"]
      hosts: ["127.0.0.1"]
      verbosity: info 

hosts settings is if your kibana runs locally with the elasticsearch. change it to the right host.

here I am migrating from elk 2.4 to es 6.2.1 , and I use RoR entreprise.
for now I still have prompt_for_basic_auth : true for compatibility and testing purpose, but I will set it to false in a few.

hope it helps you.