cross-site inclusion (XSSI) of files in jupyter-server

Impact

Improper cross-site credential checks on /files/ URLs could allow exposure of certain file contents, or accessing files when opening untrusted files via "Open image in new tab".

Patches

Jupyter Server 2.7.2

Workarounds

Use lower performance --ContentsManager.files_handler_class=jupyter_server.files.handlers.FilesHandler, which implements the correct checks.

References

Upstream patch for CVE-2019-9644 was not applied completely, leaving part of the vulnerability open.

Vulnerability reported by Tim Coen via the [bug bounty program](https://app.intigriti.com/programs/jupyter/jupyter/detail) [sponsored by the European Commission](https://commission.europa.eu/news/european-commissions-open-source-programme-office-starts-bug-bounties-2022-01-19_en) and hosted on the [Intigriti platform](https://www.intigriti.com/).