---
id: "CVE-2026-118243"
kind: "vulnerability"
aliases: ["CVE-2026-118243", "GHSA-jqgh-w3cc-7jqw"]
title: "Highcharts Dashboards: `__proto__` data table id writes sync listeners to `Object.prototype`"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "package"
products: [{"name": "@highcharts/dashboards", "fixed": ["4.2.2"], "affected": ">= 1.0.0, <= 4.2.1", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["cwe-1321", "dashboards", "frontend", "highcharts", "javascript", "package"]
not_affected_if: ["default-config", "sync-disabled", "trusted-config-only"]
published_at: "2026-10-28T18:17:15+00:00"
first_seen_at: "2026-10-28T18:34:33+00:00"
updated_at: "2026-10-28T19:56:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118243", "first_seen_at": "2026-10-28T18:34:33+00:00"}, {"source": "ghsa", "url": "https://github.com/advisories/GHSA-jqgh-w3cc-7jqw", "first_seen_at": "2026-10-28T19:56:29+00:00"}]
---

# Highcharts Dashboards: `__proto__` data table id writes sync listeners to `Object.prototype`

Highcharts Dashboards stores sync listener state in plain objects keyed by DataTable ID, so a table ID of __proto__ supplied through dataPool configuration writes an enumerable property onto Object.prototype. The polluted property is visible on every object and can make lasting sync states throw, breaking features such as extremes synchronization.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- npm:@highcharts/dashboards affected >= 1.0.0, <= 4.2.1 fixed 4.2.2

## How to check

- Check the installed Highcharts version with `npm ls highcharts` or the version in the loaded `highcharts.js` header; versions from 1.0.0 up to but not including 4.2.2 are affected.
- Review dashboard configuration for `dataPool` connectors whose table IDs come from untrusted input.

## Fix

- Upgrade Highcharts (including Highcharts Dashboards) to `4.2.2`.
- Until upgraded, do not accept dashboard or dataPool configuration from untrusted sources.

## Timeline

- 2026-10-28T18:34:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118243
- 2026-10-28T19:56:29+00:00 ghsa https://github.com/advisories/GHSA-jqgh-w3cc-7jqw

## From the sources

### Impact
The data cursor keeps its listener and state bookkeeping in plain objects keyed by data table id, so a table id of `__proto__` supplied in the `dataPool` connector configuration resolves to `Object.prototype` when a sync registers its listeners, and the registration creates a property on `Object.prototype` named after the sync state and holding the internal listener array. The property name begins with a state prefix fixed by the library, to which the sync `group` option can append an attacker-chosen suffix, and its value is the library's own listener array, but the property is enumerable and visible on every object in the page, and emitting a lasting state for that table id then throws, so syncs that keep lasting states, such as `extremes`, stop working. Exploitation requires that untrusted data reach the Dashboards configuration and that a sync such as `highlight` or `extremes` be enabled on a component using that table, which the same configuration can do. No user interaction is required beyond loading the board.

The injected property is inert until other code on the page reads or enumerates it, so consequences depend on the consuming application.

### Workarounds
**Drop-in fix - for any Highcharts Dashboards versions affected (1.0.0-4.2.1).**
Add the below IIFE to run after Highcharts Dashboards is loaded. 

```
!function(t){if(t&&t.DataCursor&&t.DataTable){var e=t.DataCursor.prototype,r=t.DataTable.prototype;e.tableIdPollutionPatched||(e.tableIdPollutionPatched=!0,null!==Object.getPrototypeOf((new t.DataCursor).listenerMap)&&['addListener','emitCursor','remitCursor','removeListener'].forEach(function(t){var r=e[t];r&&(e[t]=function(){var t;return t=this,['listenerMap','stateMap'].forEach(function(e){var r,a=t[e];a&&null!==Object.getPrototypeOf(a)&&(r=Object.create(null),Object.keys(a).forEach(function(t){r[t]=a[t]}),t[e]=r)}),r.apply(this,arguments)})}),'__proto__'!==new t.DataTable({id:'__proto__'}).id||Object.getOwnPropertyDescriptor(r,'id')||Object.defineProperty(r,'id',{configurable:!0,enumerable:!0,get:function(){return this.safeTableId},set:function(e){'__proto__'!==e&&'constructor'!==e||(e=t.uniqueKey(),this.autoId=!0),this.safeTableId=e}}))}}(Dashboards);
```

[Live demo & testing](https://jsfiddle.net/BlackLabel/jwqazb51/)

### 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](https://www.highcharts.com/docs/dashboards/installation).

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