CVE-2021-41247

JupyterHub is an open source multi-user server for Jupyter notebooks. In
affected versions users who have multiple JupyterLab tabs open in the same
browser session, may see incomplete logout from the single-user server, as
fresh credentials (for the single-user server only, not the Hub) reinstated
after logout, if another active JupyterLab session is open while the logout
takes place. Upgrade to JupyterHub 1.5. For distributed deployments, it is
jupyterhub in the user environment that needs patching. There are no
patches necessary in the Hub environment. The only workaround is to make
sure that only one JupyterLab tab is open when you log out.