[DOCS] Added _xpack_security internal user (elastic/x-pack-elasticsearch#2541)
Original commit: elastic/x-pack-elasticsearch@d565d7232c71e1eb6cea1c341eafd9954e33cfb5
@@ -154,11 +154,11 @@ be set before the user can be used.
[[internal-users]]
=== Internal Users
-{security} has two _internal_ users (`_system` and `_xpack`) that are
-responsible for the operations that take place inside an Elasticsearch cluster.
+{security} has three _internal_ users (`_system`, `_xpack`, and `_xpack_security`)
+that are responsible for the operations that take place inside an {es} cluster.
These users are only used by requests that originate from within the cluster.
-For this reason, they cannot be used to authenticate against the API, and there
+For this reason, they cannot be used to authenticate against the API and there
is no password to manage or reset.
From time-to-time you may find a reference to one of these users inside your
