Highcharts JS is a JavaScript charting library based on SVG. From 1.0.0 until 4.2.3, Highcharts Dashboards edit mode parses fullscreen language labels as HTML rather than inserting them as text. An attacker who controls Dashboards language options can supply markup with event handlers, which execute in the hosting page origin when the fullscreen control is rendered. The label is reachable only when edit mode is enabled and viewFullscreen is present in the context-menu items. This issue is fixed in 4.2.3.

Affected: npm: @highcharts/dashboards

### Impact The edit mode fullscreen labels are parsed as HTML when the corresponding control is rendered. An attacker who controls the Dashboards language options can supply markup carrying event handlers, which then execute in the origin of the page hosting the dashboard. Exploitation requires that untrusted data reach the Dashboards language configuration and that the affected control be rendered. Script running this way has the same access to page data, storage and session state as the hosting application.

### Workarounds

Until you can upgrade, replace `Fullscreen.prototype.setButtonText` atapplication startup. The replacement is the original method with `textContent` in place of `innerHTML`.

#### If you install Dashboards from npm

Import the module once, before any board is created.

```js import Fullscreen from '@highcharts/dashboards/es-modules/Dashboards/EditMode/Fullscreen.js';

Fullscreen.prototype.setButtonText = function () { const editMode = this.board.editMode, button = editMode?.tools.contextMenu?.items.viewFullscreen;

if (button?.innerElement) { const lang = editMode.lang;

button.innerElement.textContent = (this.isOpen ? lang.exitFullscreen : lang.viewFullscreen) || ''; } }; ```

#### If you load Dashboards from a `<script>` tag

The same replacement, taking `Fullscreen` from the global namespace. It must run after `modules/layout` and before any board is created.

```html <script src="https://code.highchar…