An XSS vulnerability exists in JupyterLab that allows a crafted overrides.json settings file to inject and execute JavaScript in the user's browser session. The injected code runs with the user's access rights and can read, modify, or delete notebooks, access files, and execute arbitrary code against the notebook server and its connected kernels. This flaw is classified as a severe XSS (CWE-79) combined with insecure handling of text (CWE-116).

JupyterLab versions starting with 3.3.0 up until the release of 4.5.10 and 4.6.2 are affected. The security fixes are incorporated in JupyterLab 4.5.10 and 4.6.2; any earlier releases, including the interim 4.5.x and 4.6.x branches, remain vulnerable.

The CVSS score of 8.6 indicates a high severity. With no EPSS data available, the probability of exploitation cannot be quantified. The likely attack vector is local or shared: a user who imports a malicious overrides.json or an attacker who can place such a file in a shared settings directory can trigger the flaw. Because the malicious payload runs with the victim’s credentials inside the browser, the risk includes full remote code execution on the host system. The vulnerability is not listed in the CISA KEV catalog.