Highcharts Dashboards: `chartConstructor` is an unchecked lookup into the Highcharts namespace

Impact

The Highcharts component uses the value of chartConstructor to select a function from the Highcharts namespace and invokes it with the component's container element and its chartOptions, without checking the value against the supported chart constructors. An attacker who controls the dashboard configuration can therefore name any other public member of that namespace; utility functions in that namespace copy the supplied options onto the container element as properties or attributes, so markup and event handlers carried in chartOptions land in the page and run in the origin of the page hosting the dashboard. Exploitation requires that untrusted data reach the Dashboards component configuration. No user interaction is required beyond rendering the board.

Workarounds

If your board configuration comes from a source you do not fully control, paste this snippet right after importing libraries:

(function () {
    const HighchartsComponent =
        Dashboards && Dashboards.HighchartsComponent;

    if (!HighchartsComponent || !HighchartsComponent.prototype.createChart) {
        return; // HighchartsComponent not loaded
    }

    const allowedConstructors = [
        'chart',
        'stockChart',
        'mapChart',
        'ganttChart'
    ];
    const originalCreateChart = HighchartsComponent.prototype.createChart;

    HighchartsComponent.prototype.createChart = function () {
        if (allowedConstructors.indexOf(this.chartConstructor) === -1) {
            this.chartConstructor = 'chart';
        }

        return originalCreateChart.apply(this, arguments);
    };
}());

Obtaining the patched version

The patched releases are available from all the usual distribution channels. With npm, upgrade the affected package to the patched version listed above, for example npm install @highcharts/dashboards@4.2.2. If you load Highcharts Dashboards from a CDN, use a versioned URL, for example https://code.highcharts.com/dashboards/4.2.2/dashboards.js. For more on each installation method, see the installation guide.