In the Query Engine in Couchbase Server 6.5.x and 6.6.x through 6.6.1, Common Table Expression queries were not correctly checking the user's permissions, allowing read-access to resources beyond what those users were explicitly allowed to access.
https://www.couchbase.com/resources/security#SecurityAlerts
https://docs.couchbase.com/server/current/release-notes/relnotes.html