An issue was discovered in Octopus before 3.17.7. When the special Guest user account is granted the CertificateExportPrivateKey permission, and Guest Access is enabled for the Octopus Server, an attacker can sign in as the Guest account and export Certificates managed by Octopus, including the private key.
In Octopus before 3.17.7, an authenticated user who was explicitly granted the permission to invite new users (aka UserInvite) can invite users to teams with escalated privileges.