CVE-2026-118132 in NextChat
Summary
by MITRE • 10/27/2026
NextChat version 2.16.1 contains a client‑side cross‑site scripting (XSS) vulnerability in the Plugin Editor due to unsafe rendering of externally supplied OpenAPI plugin schema content. When a plugin schema is loaded from a remote URL, the returned content is stored in plugin.content and later rendered using React’s dangerouslySetInnerHTML without proper sanitization. An attacker can host a malicious OpenAPI schema containing HTML or JavaScript markup and trick a user into loading it through the Plugin Editor, resulting in arbitrary JavaScript execution in the NextChat origin. Successful exploitation allows access to JavaScript‑readable cookies and other client‑side data associated with the NextChat application.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in NextChat version 2.16.1 represents a significant security flaw within its Plugin Editor functionality, specifically categorized as a stored or reflected cross-site scripting (XSS) attack vector depending on how the schema is persisted and served. The core technical issue stems from the application's handling of OpenAPI plugin schemas sourced from external URLs. When an administrator or user configures a new plugin by pointing to a remote specification file, NextChat retrieves this content and stores it within the plugin.content property. Subsequently, when the interface renders details about this plugin for editing or viewing purposes, the framework utilizes React's dangerouslySetInnerHTML API to inject the schema data directly into the DOM without applying any sanitization filters. This approach bypasses React’s default HTML escaping mechanisms, allowing raw HTML and JavaScript code embedded within the OpenAPI JSON structure to execute in the context of the victim’s browser session.
From a classification perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism involves the unsafe rendering of user-controllable input, where the application fails to validate or encode special characters that could be interpreted as executable code by the browser's JavaScript engine. Furthermore, this flaw can be mapped to MITRE ATT&CK technique T1059.007, which covers Command and Scripting Interpreter via JavaScript, specifically within a web-based context. The attacker’s role is critical in this exploitation chain; they must host a malicious OpenAPI schema file on a server under their control. This file contains crafted JSON content where string values include script tags or event handlers such as onload attributes that trigger arbitrary code execution upon parsing and rendering by the vulnerable application component.
The operational impact of successfully exploiting this vulnerability is severe, primarily due to its client-side nature within an administrative tool like NextChat. Once the malicious schema is loaded through the Plugin Editor interface, the injected JavaScript executes with the same privileges as legitimate scripts running on the NextChat domain. This grants the attacker full access to session cookies, local storage data, and other sensitive information stored in the browser’s memory associated with the application. In many deployment scenarios, these credentials or tokens may provide elevated access levels, potentially allowing the attacker to impersonate valid users, exfiltrate conversation history, manipulate plugin configurations, or even pivot further into backend systems if session cookies are used for authentication against API endpoints. The lack of Content Security Policy (CSP) restrictions in some default configurations can exacerbate this risk by permitting script execution from any source.
Mitigation strategies should focus on immediate remediation and long-term architectural improvements. For NextChat version 2.16.1, users are advised to upgrade to a patched release where the developers have implemented proper input sanitization before rendering plugin content via dangerouslySetInnerHTML. Libraries such as DOMPurify can be integrated into the frontend codebase to strip out dangerous tags and attributes while preserving necessary formatting. Additionally, implementing strict Content Security Policy headers that restrict script execution to trusted sources only would provide a robust defense-in-depth layer, preventing inline scripts from executing even if they are injected into the DOM. Administrators should also enforce validation on plugin schema URLs at ingestion time, ensuring that only whitelisted domains can be used for loading external plugins, thereby reducing the attack surface available to potential adversaries seeking to inject malicious content through this vector.