[jupyterhub] Cross-Site Request Forgery in JupyterHub

JupyterHub 1.1.0 allows CSRF in the admin panel via a request that lacks an _xsrf field, as demonstrated by a /hub/api/user request (to add or remove a user account).

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-36191
• https://github.com/jupyterhub/jupyterhub/issues/3304
• https://github.com/jupyterhub/jupyterhub/releases
• https://github.com/advisories/GHSA-7xx3-qp5w-fw96
• https://github.com/pypa/advisory-database/tree/main/vulns/jupyterhub/PYSEC-2021-67.yaml