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EUVD-2026-265158

2026-10-06T16:03:25.230372+00:00

EUVD-2026-265158

fkie_cve-2026-21872

2026-10-06T16:03:25.230407+00:00

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.

GHSA-m7j5-rq9j-6jj9 — NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-provided links

2026-10-06T16:03:25.230439+00:00

Affected: PyPI: nicegui

### Summary

An unsafe implementation in the `click` event listener used by `ui.sub_pages`, 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 `sub_pages_navigate` event is emitted. https://github.com/zauberzeug/nicegui/blob/59fa9424c470f1b12c5d368985fa36e21fda706b/nicegui/elements/sub_pages.js#L41-L63

2. SubPagesRouter (used by ui.sub_pages), lisnening on `sub_pages_navigate`, `_handle_navigate` runs. https://github.com/zauberzeug/nicegui/blob/59fa9424c470f1b12c5d368985fa36e21fda706b/nicegui/sub_pages_router.py#L18-L22

3. `_handle_navigate` runs `run_javascript` with f-string substituting `self.current_path` which is simply surrounded by double-quotes. The string context can be broken out easily.

https://github.com/zauberzeug/nicegui/blob/59fa9424c470f1b12c5d368985fa36e21fda706b/nicegui/sub_pages_router.py#L73-L88

### PoC

The minimal PoC boils down to this:

```py from nicegui import ui

ui.sub_pages({'/': lambda: ui.link('Go to XSS', '/"+alert(1)+"')})

ui.run() ```

However, it is more likely that the attack takes place with attacker-controlled input, for which this shows it:

```py from nicegui import app, ui

ui.sub_pages({'/': lambda: ui.label('Hello, World!')})

ui.textarea('Markdown content').bind_value(app.storage.general, 'markdown_content')

ui.markdown().bind_content_from(app.storage.general, 'markdown_content')

ui.run() ```

Vulnerable input is `[X…

PYSEC-2026-1701 — NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-provided links

2026-10-06T16:03:25.230493+00:00

Affected: PyPI: nicegui

### Summary

An unsafe implementation in the `click` event listener used by `ui.sub_pages`, 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 `sub_pages_navigate` event is emitted. https://github.com/zauberzeug/nicegui/blob/59fa9424c470f1b12c5d368985fa36e21fda706b/nicegui/elements/sub_pages.js#L41-L63

3. `_handle_navigate` runs `run_javascript` with f-string substituting `self.current_path` which is simply surrounded by double-quotes. The string context can be broken out easily.

https://github.com/zauberzeug/nicegui/blob/59fa9424c470f1b12c5d368985fa36e21fda706b/nicegui/sub_pages_router.py#L73-L88

### PoC

The minimal PoC boils down to this:

```py from nicegui import ui

ui.sub_pages({'/': lambda: ui.link('Go to XSS', '/"+alert(1)+"')})

ui.run() ```

However, it is more likely that the attack takes place with attacker-controlled input, for which this shows it:

```py from nicegui import app, ui

ui.sub_pages({'/': lambda: ui.label('Hello, World!')})

ui.textarea('Markdown content').bind_value(app.storage.general, 'markdown_content')

ui.markdown().bind_content_from(app.storage.general, 'markdown_content')

ui.run() ```

Vulnerable input is `[X…