CVE-2026-50758: Next-AI-Draw-IO XSS Vulnerability

CVE-2026-50758 Overview

CVE-2026-50758 is a Cross-Site Scripting (XSS) vulnerability affecting DayuanJiang next-ai-draw-io version 0.4.13. The flaw resides in the handling of the mcp parameter, which fails to sanitize user-supplied input before rendering it in the browser context. A remote attacker can craft a malicious URL or payload that, once interacted with by a victim, executes arbitrary script code in the user's session. The issue is classified under [CWE-79] Improper Neutralization of Input During Web Page Generation.

Critical Impact
Successful exploitation allows an attacker to execute arbitrary JavaScript in the victim's browser, enabling session hijacking, credential theft, and unauthorized actions against the next-ai-draw-io application.

Affected Products

DayuanJiang next-ai-draw-io version 0.4.13

Discovery Timeline

2026-07-21 - CVE-2026-50758 published to NVD
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-50758

Vulnerability Analysis

The vulnerability is a reflected or stored Cross-Site Scripting flaw in the next-ai-draw-io application, an AI-assisted diagramming tool built on the draw.io ecosystem. The mcp parameter accepts attacker-controlled input that reaches a rendering context without proper output encoding or input sanitization. When a victim loads a crafted request, the injected payload executes with the privileges of the current user session.

The [CWE-79] classification indicates that the application does not neutralize special characters such as <, >, and quote marks before returning them in HTML output. Because the attack vector is network-based and requires user interaction, delivery typically occurs through a phishing link or embedded reference on an attacker-controlled page.

Root Cause

The root cause is insufficient input validation and output encoding on the mcp parameter within the next-ai-draw-io request handling logic. User-supplied data flows into an HTML or JavaScript sink without being processed through a context-aware encoding routine. Frameworks that render this parameter into the DOM without escaping HTML entities allow script tags or event handlers to be interpreted as executable code.

Attack Vector

The attack is initiated remotely over the network and requires no privileges on the target system. An attacker crafts a URL containing a malicious mcp parameter value and delivers it through phishing, chat platforms, or embedded links. When the victim clicks the link and interacts with the application, the payload executes in the browser context. The vulnerability affects confidentiality and integrity of user data but does not directly impact application availability. For technical specifics, refer to the GitHub CVE-2026-50758 Documentation and the GitHub Issue Discussion.

No verified proof-of-concept code is published in the enriched advisory data. Reviewers should consult the referenced GitHub issues for reproduction details.

Detection Methods for CVE-2026-50758

Indicators of Compromise

HTTP requests to next-ai-draw-io endpoints containing mcp parameter values with <script>, javascript:, or HTML event handler attributes such as onerror= or onload=.
URL-encoded payloads in the mcp parameter containing sequences like %3Cscript%3E or %22%3E%3C.
Anomalous outbound requests from user browsers to attacker-controlled domains after visiting next-ai-draw-io links.

Detection Strategies

Deploy Web Application Firewall (WAF) rules that inspect the mcp query parameter for XSS signatures and block requests containing script-like content.
Enable Content Security Policy (CSP) violation reporting to surface inline script execution attempts in the browser.
Review application access logs for repeated requests to the same endpoint with varied mcp parameter payloads, which may indicate exploitation attempts.

Monitoring Recommendations

Aggregate web server and reverse proxy logs into a centralized log platform and alert on parameter values containing HTML or JavaScript syntax.
Monitor endpoint browser telemetry for unexpected script execution originating from the next-ai-draw-io application domain.
Track user reports of unexpected pop-ups, redirects, or session anomalies while using the application.

How to Mitigate CVE-2026-50758

Immediate Actions Required

Restrict access to next-ai-draw-io version 0.4.13 deployments until a patched release is available.
Instruct users to avoid clicking untrusted links that reference the next-ai-draw-io application.
Apply a Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.

Patch Information

No vendor patch is referenced in the enriched CVE data at the time of publication. Administrators should monitor the GitHub Issue Report and the upstream repository for a fixed release beyond version 0.4.13.

Workarounds

Deploy WAF rules that block or sanitize the mcp parameter for requests targeting next-ai-draw-io endpoints.
Enforce a strict Content Security Policy header, for example Content-Security-Policy: default-src 'self'; script-src 'self', to prevent execution of injected inline scripts.
Configure reverse proxies to reject requests containing HTML control characters such as <, >, and " in the mcp parameter.

bash

# Example NGINX rule to block XSS payloads in the mcp parameter
if ($arg_mcp ~* "(<|%3C)script|javascript:|onerror=|onload=") {
    return 403;
}