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

Summary An unsafe implementation in the click event listener used by ui.subpages, combined with attacker-controlled link rendering on the page, causes an XSS when the user actively clicks on the link. Details 1. On click, eventually subpagesnavigate event is emitted...

Cross-site Scripting (XSS)

Overview nicegui is a Create web-based user interfaces with Python. The nice way. Affected versions of this package are vulnerable to Cross-site Scripting XSS via the ui.subpages function. An attacker can execute JavaScript in the context of the user's browser by tricking a user into clicking a...

CVE-2026-21873 Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`

NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.subpages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been...

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

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.subpages, 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 versi...

PT-2026-2111

Name of the Vulnerable Software and Affected Versions NiceGUI versions 2.22.0 through 3.4.1 Description NiceGUI is a Python-based UI framework susceptible to a cross-site scripting XSS issue. The problem stems from an unsafe implementation within the click event listener used by ui.sub pages,...