CVE-2021-22137: Improper Preservation of Permissions

In Elasticsearch versions before 7.11.2 and 6.8.15 a document disclosure flaw was found when Document or Field Level Security is used. Search queries do not properly preserve security permissions when executing certain cross-cluster search queries. This could result in the search disclosing the existence of documents the attacker should not be able to view. This could result in an attacker gaining additional insight into potentially sensitive indices.