Highcharts Dashboards: editableOptions.propertyPath writes to Object.prototype

Highcharts JS is a JavaScript charting library based on SVG. From 1.0.0 until 4.2.2, Highcharts Dashboards edit mode walks editableOptions propertyPath segments without rejecting prototype-related keys. An attacker who controls editableOptions can provide a path through proto or constructor, and a user's edit writes the configured value onto Object.prototype. The property then becomes visible to JavaScript throughout the page, with consequences determined by the consuming application. This issue is fixed in 4.2.2.