CVE-2026-118252 in Highcharts
Summary
by MITRE • 10/28/2026
Highcharts JS is a JavaScript charting library based on SVG. From 1.0.0 until 4.2.3, Highcharts Dashboards edit-mode sidebar parses component language strings as HTML rather than inserting them as text. An attacker who controls the Dashboards language configuration can provide markup containing event handlers, which execute in the hosting page origin when a user opens the edit-mode sidebar and the affected labels render. This issue is fixed in 4.2.3.
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Analysis
by VulDB Data Team • 10/28/2026
The vulnerability identified within Highcharts JS versions ranging from 1.0.0 to 4.2.3 represents a critical server-side input validation failure that manifests as a client-side cross-site scripting flaw. Specifically, the defect resides in the edit-mode sidebar functionality of the Highcharts Dashboards module. When this interface is rendered, it processes component language strings by interpreting them as HTML markup rather than treating them as plain text data. This architectural decision allows for the injection and subsequent execution of arbitrary JavaScript code if an attacker can influence the content of these language configuration files. The root cause lies in the lack of proper encoding or sanitization when rendering user-controlled or externally sourced string values into the DOM, a classic oversight that violates fundamental secure coding principles regarding data handling.
From a technical perspective, this flaw enables stored cross-site scripting attacks where malicious markup containing event handlers is embedded within the dashboard configuration. When an authenticated user accesses the edit-mode sidebar and triggers the rendering of affected labels, the browser parses the injected HTML. Because the code executes in the context of the hosting page origin, it inherits all associated privileges, including access to cookies, session tokens, local storage data, and the ability to perform actions on behalf of the victim. This effectively bypasses same-origin policy protections, allowing an attacker to steal sensitive information or manipulate the application state without requiring additional social engineering beyond the initial configuration injection.
The operational impact is severe for any organization relying on Highcharts Dashboards where dashboard configurations are subject to modification by users with sufficient privileges to edit language settings or component properties. An adversary who gains control over these configuration parameters can persist malicious scripts that execute every time a victim opens the sidebar, creating a persistent threat vector. This compromises the confidentiality and integrity of user sessions and potentially allows for further network pivoting if internal resources are accessible from the dashboard's origin. The vulnerability underscores the risks associated with dynamic content rendering in web applications, particularly when dealing with rich text or configuration data that may contain untrusted input.
Mitigation strategies must prioritize immediate patching to version 4.2.3 or later, where this parsing behavior has been corrected to safely handle language strings as plain text. For environments unable to upgrade immediately, defensive coding practices should be implemented at the application layer by ensuring all user-supplied data is strictly encoded before being inserted into HTML contexts. Input validation frameworks that enforce allow-listing of permitted characters can also reduce exposure. Furthermore, implementing Content Security Policy headers with strict directives against inline script execution provides a robust defense-in-depth measure that would neutralize the impact even if such injection attempts occur in other parts of the application ecosystem.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-79, which classifies improper neutralization of input during web page generation as cross-site scripting. In terms of tactical mapping within the MITRE ATT&CK framework, this flaw facilitates initial access and credential theft through techniques associated with client-side code injection. The ability to execute scripts in the victim's browser context directly supports data exfiltration and session hijacking tactics commonly employed by threat actors targeting web-based analytics and dashboarding platforms.