{"id":"CVE-2026-118243","kind":"vulnerability","aliases":["CVE-2026-118243","GHSA-jqgh-w3cc-7jqw"],"related":[],"title":"Highcharts Dashboards: `__proto__` data table id writes sync listeners to `Object.prototype`","description":"### Impact\nThe 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.\n\nThe injected property is inert until other code on the page reads or enumerates it, so consequences depend on the consuming application.\n\n### Workarounds\n**Drop-in fix - for any Highcharts Dashboards versions affected (1.0.0-4.2.1).**\nAdd the below IIFE to run after Highcharts Dashboards is loaded. \n\n```\n!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);\n```\n\n[Live demo & testing](https://jsfiddle.net/BlackLabel/jwqazb51/)\n\n### Obtaining the patched version\nThe 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).","summary":"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.","severity":"medium","cvss":5.3,"epss":null,"exploited":false,"exploited_at":null,"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"],"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.\n- Review dashboard configuration for `dataPool` connectors whose table IDs come from untrusted input.","fix":"- Upgrade Highcharts (including Highcharts Dashboards) to `4.2.2`.\n- Until upgraded, do not accept dashboard or dataPool configuration from untrusted sources.","status":"open","published_at":"2026-10-28T18:17:15+00:00","first_seen_at":"2026-10-28T18:34:33+00:00","triaged_at":"2026-10-28T18:35:08+00:00","updated_at":"2026-10-28T19:56:29+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-10-28T18:35:08Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Highcharts (including Highcharts Dashboards) to `4.2.2`.\n- Until upgraded, do not accept dashboard or dataPool configuration from untrusted sources.","reach":"unknown","title":"Highcharts Dashboards: crafted table ID pollutes JavaScript object prototype","impact":"low","summary":"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.","category":"package","nicknames":[],"who_cares":["highcharts","javascript","dashboards","frontend"],"confidence":0.6,"needs_auth":"unknown","worst_case":"Polluted prototype breaks sync features and page behavior in the browser.","analyst_note":"Sources do not state the exact fixed-version advisory link or whether any exploitation beyond local prototype pollution is possible; verify the Highcharts 4.2.2 release notes.","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.\n- Review dashboard configuration for `dataPool` connectors whose table IDs come from untrusted input.","needs_analyst":true,"not_affected_if":["default-config","trusted-config-only","sync-disabled"],"who_is_affected":"Teams that run Highcharts Dashboards from version 1.0.0 through 4.2.1 with component sync enabled and that load dashboard configuration which can be influenced by untrusted parties, such as user-supplied or externally stored board definitions. Boards built only from trusted, developer-authored configuration with sync off are unlikely to be exposed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000693,"input_tokens":3433,"output_tokens":700,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-118243':14A,22A '-1321':25B '-2026':13A,21A '/blacklabel/jwqazb51/)':406C '/dashboards/4.2.2/dashboards.js':456C '/docs/dashboards/installation).':469C '0':309C,380C,382C,397C '1.0.0':283C '4.2.1':284C '4.2.2':439C '7jqw':19A 'add':285C 'addlisten':315C 'affect':282C,426C 'append':158C 'applic':271C 'argument':366C 'array':138C,173C 'attack':161C 'attacker-chosen':160C 'avail':415C 'begin':142C 'beyond':246C 'board':249C 'bookkeep':90C 'break':75B 'cdn':447C 'channel':421C 'chosen':162C 'code':257C 'code.highcharts.com':455C 'code.highcharts.com/dashboards/4.2.2/dashboards.js':454C 'compon':231C 'configur':53B,110C,217C,238C,379C 'connector':109C 'consequ':266C 'constructor':392C 'consum':270C 'creat':123C 'cursor':84C 'cve':12A,20A 'cwe':24B 'dashboard':2A,26B,32B,216C,280C,293C,400C,444C 'data':4A,83C,96C,213C 'datapool':52B,108C 'datat':42B 'demo':402C 'depend':267C 'distribut':420C 'drop':274C 'drop-in':273C 'e':303C,324C,327C,339C,344C,362C,389C,391C,393C,394C,399C 'e.tableidpollutionpatched':307C,308C 'emit':188C 'emitcursor':316C 'enabl':228C 'enumer':56B,178C,263C,381C 'everi':66B,182C 'exampl':435C,453C 'exploit':209C 'extrem':79B,206C,226C 'featur':76B 'fix':147C,276C 'foreach':319C,337C,354C 'frontend':27B 'function':296C,320C,329C,338C,355C,384C,388C 'get':383C 'ghsa':16A 'ghsa-jqgh-w3cc-7jqw':15A 'group':155C 'guid':466C 'highchart':1A,28B,31B,279C,292C,443C 'highcharts/dashboards':23A,438C 'highlight':224C 'hold':134C 'id':6A,43B,47B,98C,102C,195C,370C,372C,375C,378C 'iif':288C 'impact':81C 'inert':254C 'inject':251C 'instal':437C,461C,465C 'interact':243C 'intern':136C 'javascript':29B 'jqgh':17A 'jsfiddle.net':405C 'jsfiddle.net/blacklabel/jwqazb51/)':404C 'keep':85C,201C 'key':40B,94C 'last':71B,190C,202C 'librari':150C,169C 'list':432C 'listen':9A,35B,87C,119C,137C,172C 'listenermap':314C,335C 'live':401C 'load':247C,295C,442C 'make':70B 'method':462C 'name':128C,141C 'new':312C,368C 'npm':423C,436C 'null':310C,346C,351C 'object':39B,67B,93C,183C 'object.create':350C 'object.defineproperty':376C 'object.getownpropertydescriptor':373C 'object.getprototypeof':311C,347C 'object.keys':352C 'object.prototype':11A,59B,113C,127C 'obtain':407C 'onto':58B 'option':156C 'packag':30B,427C 'page':186C,260C 'patch':409C,412C,430C 'plain':38B,92C 'pollut':61B 'prefix':146C 'properti':57B,62B,125C,140C,176C,252C 'proto':3A,49B,104C,367C,371C,390C 'r':305C,323C,326C,341C,349C,357C,363C,374C,377C 'r.apply':364C 'reach':214C 'read':261C 'regist':117C 'registr':122C 'releas':413C 'remitcursor':317C 'removelisten':318C 'requir':210C,245C 'resolv':111C 'return':332C,385C 'run':290C 'see':463C 'set':387C 'state':36B,73B,89C,132C,145C,191C,203C 'statemap':336C 'stop':207C 'store':33B 'suffix':163C 'suppli':50B,105C 'sync':8A,34B,72B,116C,131C,154C,199C,221C 'synchron':80B 't.datacursor':300C,313C 't.datacursor.prototype':304C 't.datatable':301C,369C 't.datatable.prototype':306C 't.uniquekey':395C 'tabl':5A,46B,97C,101C,194C,234C 'test':403C 'this.autoid':396C 'this.safetableid':386C,398C 'throw':74B,197C 'untrust':212C 'upgrad':424C 'url':451C 'use':232C,448C 'user':242C 'usual':419C 'valu':166C 'var':302C,322C,330C,340C 'version':281C,410C,431C,450C 'visibl':64B,180C 'w3cc':18A 'work':208C 'workaround':272C 'write':7A,54B 'www.highcharts.com':468C 'www.highcharts.com/docs/dashboards/installation).':467C","nicknames":[],"mitigations":[],"who_affected":"Teams that run Highcharts Dashboards from version 1.0.0 through 4.2.1 with component sync enabled and that load dashboard configuration which can be influenced by untrusted parties, such as user-supplied or externally stored board definitions. Boards built only from trusted, developer-authored configuration with sync off are unlikely to be exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-28T18:17:15+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-118243","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-118243","severity":null,"published_at":"2026-10-28T18:17:15+00:00","modified_at":"2026-10-28T18:17:15+00:00","first_seen_at":"2026-10-28T18:34:33+00:00","fetched_at":"2026-10-28T18:34:33+00:00","note":null},{"source":"ghsa","external_id":"GHSA-jqgh-w3cc-7jqw","url":"https://github.com/advisories/GHSA-jqgh-w3cc-7jqw","severity":"medium","published_at":"2026-10-28T19:55:32+00:00","modified_at":"2026-10-28T19:55:35+00:00","first_seen_at":"2026-10-28T19:56:29+00:00","fetched_at":"2026-10-28T19:56:29+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}