Default credentials

dockerspawner is a tool to spawn JupyterHub single user servers in Docker containers. Users of JupyterHub deployments running DockerSpawner starting with 0.11.0 without specifying DockerSpawner.allowed_images configuration allow users to launch any pullable docker image, instead of restricting to only the single configured image, as intended. This issue has been addressed in commit 3ba4b665b which has been included in dockerspawner release version 13. Users are advised to upgrade. Users unable to upgrade should explicitly set DockerSpawner.allowed_images to a non-empty list containing only the default image will result in the intended default behavior.