Highcharts: dotted series.keys paths write to Object.prototype

Impact

A dot-separated key path taken from series.keys is followed without filtering the individual segments. An attacker who controls series.keys and the matching point data can use a path such as __proto__.polluted to set arbitrary properties on Object.prototype. The resulting properties are visible to all JavaScript running in the page, not only to the chart. No user interaction is required beyond rendering the chart.

The injected properties are inert until other code on the page reads them, so consequences depend on the consuming application.

Workarounds

Drop-in fix - for any versions affected (6.1.0-13.0.2). Add the below IIFE to run after Highcharts is loaded.

((H)=>{const X = H.isObject;H.Point.prototype.setNestedProperty = function setNestedProperty(t,e,i){let s=i.split(".");return s.some(t=>"__proto__"===t||"constructor"===t)||s.reduce(function(t,i,s,o){let r=o.length-1===s;return t[i]=r?e:X(t[i],!0)?t[i]:{},t[i]},t),t};})(Highcharts);

Live demo & testing

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@13.1.1. If you load Highcharts from the CDN, use the versioned URLs on code.highcharts.com, for example https://code.highcharts.com/13.1.1/highcharts.js. For more on each installation method, see the installation guide.