Elasticsearch versions 7.0.0-7.3.2 and 6.7.0-6.8.3 contain a username disclosure flaw was found in the API Key service. An unauthenticated attacker could send a specially crafted request and determine if a username exists in the Elasticsearch native realm.
A race condition flaw was found in the response headers Elasticsearch versions before 7.2.1 and 6.8.2 returns to a request. On a system with multiple users submitting requests, it could be possible for an attacker to gain access to response header containing sensitive data from another user.