What’s Vulnerable › Vulnerabilities

CVE-2026-67338: JupyterLab before 4.5.9 Stored XSS via Extension Manager

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-01 · updated 2026-10-08
• Weakness: CWE-84

Description

JupyterLab before 4.5.9 contains a stored cross-site scripting vulnerability in the Extension Manager that fails to validate URI protocols in package metadata URLs. Attackers can publish malicious PyPI packages with javascript: URLs in project metadata that execute arbitrary JavaScript in the JupyterLab origin when users click the extension name.

Affected products

• jupyterlab: before 4.5.9 — fixed in 4.5.9

How to fix

Upgrade to a fixed version: jupyterlab 4.5.9. Check the vendor advisory for mitigations.

References

• https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6
• https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12
• https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-vmhf-c436-hxj4
• https://www.vulncheck.com/advisories/jupyterlab-before-stored-xss-via-extension-manager

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