CVE-2026-120988 in billboard.js
Summary
by MITRE • 11/03/2026
billboard.js before 4.1.3 allows an attacker to execute malicious JavaScript due to improper sanitization of series ids during legend template rendering.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in billboard.js versions prior to 4.1.3 represents a critical security flaw rooted in the framework's handling of dynamic content generation, specifically within the legend component. Billboard.js is a popular JavaScript charting library that allows developers to create interactive visualizations for web applications. The core issue arises from improper sanitization of series identifiers when these identifiers are utilized within custom template strings for rendering legends. In many modern web development scenarios, particularly those involving dynamic data visualization, it is common practice to allow users or administrators to define how chart elements like legends appear by providing custom HTML templates. When the library processes a user-supplied series id and injects it directly into such a template without adequate validation or encoding, it creates an opportunity for Cross-Site Scripting attacks. This flaw indicates that the input sanitization logic failed to distinguish between safe alphanumeric identifiers and potentially malicious script payloads embedded within them.
From a technical perspective, this vulnerability is classified under CWE-79, which covers Improper Neutralization of Input During Web Page Generation commonly known as Stored or Reflected Cross-Site Scripting. The attack vector typically involves an attacker crafting a specific series id that contains executable JavaScript code rather than a standard identifier string. When the billboard.js library renders the legend using this tainted input within its template engine, the browser interprets and executes the injected script in the context of the victim's session. This execution occurs without any additional user interaction beyond viewing the chart, making it particularly dangerous as it can be triggered simply by loading a page containing the maliciously crafted visualization. The lack of strict type checking or output encoding allows arbitrary code to run with the same privileges and permissions as the legitimate application scripts.
The operational impact of this vulnerability is severe for any web application relying on billboard.js for data presentation where legend customization is enabled. Successful exploitation can lead to full session hijacking, allowing attackers to steal sensitive cookies, authentication tokens, or other credentials stored in browser storage. Furthermore, it enables phishing attacks within the context of the trusted domain, potentially tricking users into revealing further information or performing unintended actions. In enterprise environments, this could facilitate lateral movement if combined with other vulnerabilities, as the attacker gains a foothold to execute arbitrary commands on behalf of authenticated users. The scope of impact is limited to clients who view charts with maliciously crafted series ids in their legends, but given the widespread use of such libraries in dashboards and analytics platforms, the potential blast radius can be significant across multiple user sessions.
To mitigate this risk, organizations must immediately upgrade billboard.js to version 4.1.3 or later, where the developers have implemented stricter sanitization protocols for series identifiers used in legend templates. For applications that cannot update immediately due to dependency constraints, a temporary workaround involves implementing custom input validation on the server side before passing any series data to the frontend library. This validation should ensure that all series ids consist only of expected alphanumeric characters and do not contain special HTML or JavaScript symbols such as angle brackets, quotes, or script tags. Additionally, developers should review their usage of template engines within billboard.js configurations to ensure that no user-controlled input is directly interpolated into HTML structures without proper encoding. Adhering to these practices aligns with OWASP recommendations for preventing injection flaws and ensures the integrity of client-side rendering processes.
In terms of threat intelligence frameworks, this vulnerability maps to MITRE ATT&CK technique T1059, specifically sub-technique 007 which covers JavaScript execution. This classification highlights how attackers leverage scripting languages within web applications to achieve their objectives without relying on external binaries or system-level exploits. Security teams should monitor for unusual patterns in chart rendering requests that might indicate probing for this specific injection point. Regular security assessments and code reviews focusing on dynamic content generation are essential to identify similar flaws in other components of the application stack. By treating all user-supplied data as untrusted until explicitly validated, developers can significantly reduce the attack surface associated with client-side libraries like billboard.js.