CVE-2026-6658
Description
A vulnerability in jupyter/nbconvert versions <= 7.17.0 allows for Cross-site Scripting (XSS) via unsanitized `text/vnd.mermaid` output in HTML exports. The `data_mermaid` block in `share/templates/lab/base.html.j2` renders `text/vnd.mermaid` cell output directly into HTML without escaping, enabling attackers to inject arbitrary HTML/JavaScript by breaking out of the `<pre>` tag. This vulnerability impacts any server using nbconvert to render notebooks as HTML, allowing attackers to execute arbitrary JavaScript in the context of users viewing the HTML export.
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| nbconvertPyPI | v ≤ 7.17.0 | — |
| jupyter jupyter/jupyter | v ≤ latest | — |
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