CVE-2026-21872 – NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-provided links

CVE ID : CVE-2026-21872

Published : Jan. 8, 2026, 10:15 a.m. | 2 hours, 12 minutes ago

Description : NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the click event listener used by ui.sub_pages, combined with attacker-controlled link rendering on the page, causes XSS when the user actively clicks on the link. This issue has been patched in version 3.5.0.

Severity: 6.1 | MEDIUM

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