Sonatype Nexus Repository 3: group repositories expose unauthorized member repositories

Sonatype Nexus Repository 3 does not check that a user account is authorized to access a repository before the repository is added as a member of a group repository. A user account that has signed in with valid credentials and holds the add or edit privilege on a group repository can add a repository that the account cannot read or browse, and then read the content of that repository through the group. The anonymous user can only do this if an administrator has explicitly granted it that privilege.