nbgrader is a system for assigning and grading notebooks. Enabling frame-ancestors: self grants any JupyterHub user the ability to extract formgrader content by sending malicious links to users with access to formgrader, at least when using the default JupyterHub configuration of enable_subdomains = False. #1915 disables a protection which would allow user Alice to craft a page embedding formgrader in an IFrame. If Bob visits that page, his credentials will be sent and the formgrader page loaded. Because Alices page is on the same Origin as the formgrader iframe, Javasript on Alices page has full access to the contents of the page served by formgrader using Bobs credentials. This issue has been addressed in release 0.9.5 and all users are advised to upgrade. Users unable to upgrade may disable frame-ancestors: self, or enable per-user and per-service subdomains with JupyterHub.enable_subdomains = True (then even if embedding in an IFrame is allowed, the host page does not have access to the contents of the frame).
The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
Resources such as files and directories may be inadvertently exposed through mechanisms such as insecure permissions, or when a program accidentally operates on the wrong object. For example, a program may intend that private files can only be provided to a specific user. This effectively defines a control sphere that is intended to prevent attackers from accessing these private files. If the file permissions are insecure, then parties other than the user will be able to access those files. A separate control sphere might effectively require that the user can only access the private files, but not any other files on the system. If the program does not ensure that the user is only requesting private files, then the user might be able to access other files on the system. In either case, the end result is that a resource has been exposed to the wrong party.