When generating a user invitation code in Octopus Server, the validity of this code can be set for a specific number of users. It was possible to bypass this restriction of validity to create extra user accounts above the initial number of invited users.
In Octopus Server after version 2018.8.2 if the Octopus Server Web Request Proxy is configured with authentication, the password is shown in plaintext in the UI.
In Octopus Deploy 2018.8.0 through 2018.9.x before 2018.9.1, an authenticated user with permission to modify deployment processes could upload a maliciously crafted YAML configuration, potentially allowing for remote execution of arbitrary code, running in the same context as the Octopus Server (for self-hosted installations by default, SYSTEM).