In affected Microsoft Windows versions of Octopus Deploy, the server can be coerced into sending server-side requests that contain authentication material allowing a suitably positioned attacker to compromise the account running Octopus Server and potentially the host infrastructure itself.
In affected versions of Octopus Deploy users of certain browsers using AD to sign-in to Octopus Server were able to bypass authentication checks and be redirected to the configured redirect url without any validation.
In affected versions of Octopus Server where access is managed by an external authentication provider, it was possible that the API key/keys of a disabled/deleted user were still valid after the access was revoked.