Highcharts Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') Vulnerability (CVE-2026-118250)
Description
Highcharts JS is a JavaScript charting library based on SVG. From 6.1.0 until 11.4.9, 12.6.1, and 3.1.0, Highcharts follows dot-separated series.keys paths without filtering each segment. An attacker who controls series.keys and matching point data can use a path through __proto__ to assign arbitrary named properties to Object.prototype. Those properties are visible to all JavaScript in the page, and no user interaction is required beyond rendering the chart. This issue is fixed in 11.4.9, 12.6.1, and 3.1.0.