PYSEC-2026-366 Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

The nbconvert HTTP handlers in jupyterserver render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their Content-Security-Policy. Combined with nbconvert.HTMLExporter's default non-sanitizing behavior, a notebook carrying an HTML payload in a displaydata outpu...

CVE-2026-44727 Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

Jupyter Server is the backend for Jupyter web applications. Prior to 2.20, the nbconvert HTTP handlers in jupyterserver render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their Content-Security-Policy. Combined with nbconvert.HTMLExporter's default...

CVE-2026-44727 Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP

Jupyter Server is the backend for Jupyter web applications. Prior to 2.20, the nbconvert HTTP handlers in jupyterserver render user-authored notebook HTML under the Jupyter origin without a sandbox directive in their Content-Security-Policy. Combined with nbconvert.HTMLExporter's default...

CVE-2026-44727

Jupyter Server (prior to 2.20) is affected by a stored XSS in the nbconvert HTML export path. The nbconvert HTTP handlers NbconvertFileHandler and NbconvertPostHandler render notebook HTML under the Jupyter origin without a sandbox directive in Content-Security-Policy, and NbconvertHTMLExporter’s...

PT-2018-14936 · Project Jupyter +2 · Jupyter Notebook +2

Name of the Vulnerable Software and Affected Versions: Jupyter Notebook versions prior to 5.7.1 Description: The issue allows for cross-site scripting XSS attacks via an untrusted notebook. This is because nbconvert responses are considered to have the same origin as the notebook server, enabling...