In affected versions of Octopus Server it was possible for a user with sufficient access to set custom headers in all server responses. By submitting a specifically crafted referrer header the user could ensure that all subsequent server responses would return 500 errors rendering the site mostly unusable. The user would be able to subsequently set and unset the referrer header to control the denial of service state with a valid CSRF token whilst new CSRF tokens could not be generated.
In affected versions of Octopus Deploy it was possible to upload files to unexpected locations on the host using an API endpoint. The field lacked validation which could potentially result in ways to circumvent expected workflows.