Vulnerability Database

352,427

Total vulnerabilities in the database

JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol — jupyterlab

Improper Neutralization of Encoded URI Schemes in a Web Page

A malicious PyPI package can place a javascript: URL in its [project.urls] metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin.

Details

One of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the homepage_url rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88.

best_guess_home_url = ( homepage_url # home_page / [project.urls] Homepage or data.get("project_url") or data.get("package_url") or documentation_url # docs_url / [project.urls] Documentation or source_url # [project.urls] Source Code or bug_tracker_url # bugtrack_url / [project.urls] Bug Tracker ) # homepage_url=best_guess_home_url {entry.homepage_url ? ( <a href={entry.homepage_url} target="_blank" rel="noopener noreferrer" ...> {entry.name} </a> ) : ( <div>{entry.name}</div> )}

Impact

An attacker needs to publish a package to PyPI (no access to the target). When the package appears in a victim's extension manager list and the victim clicks the extension name, the payload runs in the JupyterLab origin.

Preconditions: Extension Manager enabled with the default PyPI source, the malicious package appears in the victim's list/search results.

Patches

Patched in 4.5.9, commits 4e61e07 and d5d961f

  • Published: Jun 19, 2026
  • Updated: Jun 20, 2026
  • GHSA: GHSA-vmhf-c436-hxj4
  • Severity: Medium
  • Exploit:
  • CISA KEV:

No technical information available.

CWEs:

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

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