CVE-2026-21871: NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

January 8, 2026

XSS risk exists in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser.

Applications that do not pass untrusted input into ui.navigate.history.push/replace are not affected.

References

github.com/advisories/GHSA-7grm-h62g-5m97
github.com/zauberzeug/nicegui
github.com/zauberzeug/nicegui/releases/tag/v3.5.0
github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
nvd.nist.gov/vuln/detail/CVE-2026-21871

Code Behaviors & Features

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