Jupyterlab

A stored cross-site scripting (XSS) vulnerability, identified as CVE-2026-54527, in the `jupyterlab-git` JupyterLab extension (versions >= 0.30.0b3, < 0.54.0a1), specifically in `PlainTextDiff.ts`, allows an adversary with Git commit access to execute arbitrary JavaScript in a victim's browser and achieve Remote Code Execution (RCE) on the JupyterLab server by crafting a malicious filename in a Git commit that, when viewed as a rename diff, triggers the XSS payload to steal `_xsrf` cookies, open a terminal, and execute arbitrary shell commands to exfiltrate data.

An authenticated user can bypass the admin-configured `excluded_paths` security control in `jupyterlab-git` versions up to 0.53.0 by exploiting a case-sensitivity flaw on case-insensitive filesystems (e.g., macOS APFS, Windows NTFS), allowing unauthorized read access to git history and file content in explicitly excluded directories.

JupyterLab's HTML sanitizer allows execution of arbitrary commands via specially crafted HTML content in notebooks or Markdown files due to improper handling of `data-commandlinker-command` and `data-commandlinker-args` attributes.

JupyterLab versions prior to 4.5.7 do not correctly enforce the allow-list of extensions that can be installed from PyPI Extension Manager, allowing authenticated attackers to escalate privileges and potentially exfiltrate data, move laterally, and persistently compromise server infrastructure.