Next.js & React Security Scanner
10 dedicated scanners built specifically for modern JavaScript frameworks. Catch vulnerabilities that generic security tools miss entirely.
Why Framework-Specific Scanning?
Generic web security scanners were built for a different era. They test for SQL injection, directory traversal, and server misconfiguration, vulnerabilities that target traditional server-rendered applications with monolithic backends. But modern web applications built with Next.js and React have a fundamentally different architecture: they blend server-side rendering with client-side hydration, split code between server components and client components, handle routing through middleware and API routes, and manage state across multiple execution environments.
This architectural complexity creates an entirely new class of vulnerabilities that generic scanners are not designed to detect. A traditional scanner does not understand that a Next.js application might be leaking server-side environment variables into the client bundle through next.config.js misconfiguration. It does not know to check whether production source maps are accessible because it was not built with JavaScript bundling in mind. It cannot identify SSRF vulnerabilities in API routes because it does not understand Next.js's routing model. And it certainly will not catch dangerouslySetInnerHTML XSS vectors because it does not parse React component patterns.
The problem is amplified by AI-assisted development. When tools like Cursor, Bolt, Lovable, or v0 generate Next.js applications, they produce code that works functionally but often contains security patterns that a senior developer would catch during code review. The AI prioritizes making things work over making things secure, because security requirements are rarely explicit in the prompts. Client-side secret leakage, missing authentication on API routes, unvalidated URL fetching, and exposed source maps are all common in AI-generated Next.js code.
Vuln0x closes this gap with 10 dedicated scanning engines built from the ground up for Next.js and React applications. Each engine understands the framework's conventions, file structure, routing model, and rendering pipeline. Together, they catch the vulnerabilities that exist specifically because of how modern JavaScript applications are built, deployed, and served.
Dedicated Framework Scanners
Five core scanners that target the most critical Next.js and React vulnerability categories.
Source Map Exposure
Source maps are essential during development: they let your browser's DevTools show original source code instead of minified production bundles. But when source maps ship to production, they expose your entire codebase to anyone who knows where to look. An attacker can reconstruct your file structure, read your business logic, discover internal API endpoints, and identify vulnerable patterns without ever needing access to your repository.
What it catches:
- Publicly accessible .map files alongside production JavaScript bundles
- sourceMappingURL comments in minified JS that point to downloadable source maps
- Webpack and Next.js build artifacts left in the public directory after deployment
- Inline source maps embedded directly within production JavaScript files
Client-Side Secret Leakage
One of the most common mistakes in modern JavaScript development is accidentally exposing server-side secrets to the client. In Next.js, any environment variable not prefixed with NEXT_PUBLIC_ should only be available on the server. But AI code generators frequently get this wrong, placing API keys, database connection strings, and authentication secrets into client-rendered components where they become visible in the browser's network tab or bundled JavaScript.
What it catches:
- API keys for third-party services (Stripe, OpenAI, Twilio) embedded in client bundles
- Database connection strings leaked through Next.js environment variable misuse
- JWT signing secrets or OAuth client secrets exposed in browser-accessible code
- Firebase, Supabase, or AWS credentials hardcoded into React components
- Private environment variables accidentally included via misconfigured next.config.js
Authentication Logic
Authentication in Next.js applications spans multiple layers: middleware, API routes, server components, and client components. A flaw in any single layer can expose the entire application. AI-generated auth code often implements the happy path correctly but fails to handle edge cases like expired sessions, token refresh races, or direct API route access without middleware protection. This scanner examines your authentication implementation across all layers for common bypass patterns.
What it catches:
- API routes that can be called directly without passing through authentication middleware
- Session tokens stored in localStorage instead of HTTP-only cookies, exposing them to XSS
- Missing CSRF protection on state-changing API routes that rely solely on cookie authentication
- Password reset flows that do not invalidate previous reset tokens after use
XSS Detection
React's JSX escaping provides strong default protection against cross-site scripting, but it is not bulletproof. The dangerouslySetInnerHTML prop explicitly bypasses React's sanitization, and AI code generators use it frequently when rendering rich content, markdown, or HTML from APIs. This scanner identifies XSS vectors specific to React and Next.js applications, including DOM-based XSS through URL parameter injection and reflected XSS via server-side rendering of unsanitized user input.
What it catches:
- dangerouslySetInnerHTML usage with unsanitized content from user input or external APIs
- URL parameters rendered directly into the page via server components without escaping
- DOM-based XSS through window.location, document.referrer, or other DOM sources in useEffect hooks
- Reflected XSS in Next.js pages that read and render query parameters during server-side rendering
SSRF Detection
Server-Side Request Forgery is particularly dangerous in Next.js because API routes and server components execute on the server with access to internal networks. When an API route accepts a URL from the client and fetches it without validation, an attacker can use your server as a proxy to access internal services, cloud metadata endpoints (169.254.169.254), and other resources that should never be reachable from the public internet. AI-generated code frequently creates these vectors when implementing features like URL previews, webhooks, or image proxying.
What it catches:
- API routes that accept arbitrary URLs and fetch them without allowlist validation
- Server components that pass user-controlled input to fetch() or axios calls
- Redirect handlers that can be manipulated to reach internal network addresses
- Cloud metadata endpoint accessibility through URL parameter manipulation (AWS, GCP, Azure)
Common Next.js Security Mistakes
These are the most frequently detected vulnerabilities in AI-generated Next.js applications. Each one is a real exploit vector that our scanners catch automatically.
dangerouslySetInnerHTML without Sanitization
AI coding assistants frequently generate components that use dangerouslySetInnerHTML to render rich text, markdown content, or HTML from CMS systems. While this works functionally, it bypasses React's built-in XSS protection entirely. If the content source is ever compromised or accepts user input, attackers can inject arbitrary JavaScript that executes in every visitor's browser. The fix is straightforward: use a sanitization library like DOMPurify before passing content to dangerouslySetInnerHTML, or better yet, use a React-native markdown renderer that avoids raw HTML injection altogether.
// Vulnerable pattern AI tools often generate
<div dangerouslySetInnerHTML={{ __html: userContent }} />
// Safe alternative
import DOMPurify from "dompurify";
<div dangerouslySetInnerHTML={{ __html: DOMPurify.sanitize(userContent) }} />Environment Variables Leaking to the Client
Next.js has a clear convention: only variables prefixed with NEXT_PUBLIC_ are bundled into client-side JavaScript. But AI-generated code frequently references server-side variables in client components, or worse, adds them to next.config.js env configuration which exposes them to the browser bundle. This results in API keys, database URLs, and signing secrets being visible to anyone who inspects the page source or JavaScript bundles. Our scanner detects these leaks by analyzing both the HTML source and JavaScript bundles served to the client.
// Dangerous: exposes secret to client bundle
// next.config.js
module.exports = {
env: {
DATABASE_URL: process.env.DATABASE_URL, // Now in client JS!
},
};
// Safe: use server-only access
// Only access in API routes or server components
const db = new Database(process.env.DATABASE_URL);API Route SSRF via Unvalidated URLs
When AI generates API routes that fetch external resources, such as URL preview generators, image proxies, or webhook dispatchers, it rarely implements URL validation. The generated code typically accepts a URL parameter and passes it directly to fetch(), allowing attackers to specify internal network addresses, cloud metadata endpoints, or localhost services. In cloud environments, this can lead to credential theft through the instance metadata API. The scanner tests API routes for SSRF by analyzing request handling patterns and checking whether URL validation or allowlisting is implemented.
// Vulnerable: AI-generated URL preview endpoint
export async function GET(req: NextRequest) {
const url = req.nextUrl.searchParams.get("url");
const res = await fetch(url!); // SSRF!
return Response.json(await res.json());
}
// Safe: validate and restrict URLs
const ALLOWED_HOSTS = ["api.example.com", "cdn.example.com"];
const parsed = new URL(url!);
if (!ALLOWED_HOSTS.includes(parsed.hostname)) {
return Response.json({ error: "Blocked" }, { status: 403 });
}Beyond Generic Scanning
The security scanning industry was built around OWASP Top 10 categories that were defined for traditional web applications: injection flaws, broken authentication, sensitive data exposure, XML external entities, and so on. These categories remain relevant, but the attack surface of a modern Next.js application extends far beyond what these classic categories capture. Source map exposure is not injection. Client-side secret leakage is not XML external entities. SSRF through API routes is not the same as SSRF through traditional CGI scripts. These are new vulnerability classes that demand new scanning approaches.
Vuln0x does not replace your existing security tools. It complements them by covering the framework-specific blind spots that they cannot see. Run your DAST scanner, your SAST tool, and your dependency checker as you always have. Then add Vuln0x to catch the vulnerabilities that exist in the space between your application code and the framework that serves it. The combination gives you coverage that neither approach can achieve alone.
Our framework scanners are continuously updated to track changes in Next.js, React, and the broader JavaScript ecosystem. When Next.js introduces a new feature like Server Actions or Partial Prerendering, we analyze the security implications and build detection rules before the first vulnerabilities appear in production. When a new class of AI-generated code pattern emerges, such as the widespread use of dangerouslySetInnerHTML by chatbot coding assistants, we add detection coverage immediately. You are not just running a static set of checks: you are running a scanning engine that evolves alongside the frameworks you build with.
Whether you are a solo developer who shipped a Next.js project from Cursor in a weekend or an engineering team managing dozens of React applications across multiple environments, Vuln0x SecurityScanner ensures that the framework-specific vulnerabilities unique to modern JavaScript development are detected, reported, and remediated before they become attack vectors. Start with a free scan and see what generic tools have been missing.
Additional Framework Checks
Beyond the five core scanners, Vuln0x includes additional framework-aware checks embedded across the scanning suite.
API Route Security
Verifies that Next.js API routes enforce proper HTTP method restrictions, implement rate limiting headers, and do not expose sensitive error details in production responses.
Hydration Mismatch Detection
Identifies server-client rendering mismatches that can lead to content injection vulnerabilities when attackers manipulate the DOM between server render and client hydration.
Middleware Bypass Analysis
Tests whether Next.js middleware can be bypassed through path manipulation, locale prefixing, or direct API route access that skips the middleware chain entirely.
Server Action Validation
Checks that Next.js Server Actions validate and sanitize input on the server side, ensuring that client-side validation is not the only line of defense.
Data Serialization Safety
Detects unsafe serialization of server data passed to client components, preventing prototype pollution and data injection through props and page data.
Image Optimization Security
Validates that the Next.js Image component and image optimization API are configured with proper domain allowlists to prevent SSRF through image URL manipulation.
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