Credential Stuffing in Strapi

Credential stuffing in Strapi typically exploits the default authentication endpoints exposed by the admin panel and public API. Strapi's authentication system uses JWT tokens and provides endpoints like /auth/local for username/password login and /auth/local/register for user registration. These endpoints, when left unprotected or with weak rate limiting, become prime targets for credential stuffing attacks.

The most common attack pattern involves automated scripts cycling through massive credential databases against Strapi's /auth/local endpoint. Since Strapi returns different HTTP status codes for invalid credentials (401) versus valid but incorrect passwords (400), attackers can enumerate valid usernames. The default Strapi response structure includes detailed error messages like { "statusCode": 400, "message": "Bad Request: Invalid credentials", "error": "Bad Request" }, which provides attackers with immediate feedback on successful username discovery.

Strapi's admin panel authentication is particularly vulnerable because it's often accessible at /admin/auth/login and uses the same authentication logic. Attackers can target this endpoint to compromise administrator accounts, which grants full control over the Strapi CMS, including content management, user administration, and plugin configuration. The admin panel's rich interface makes it an attractive target since successful compromise provides immediate access to sensitive content and configuration.

Another manifestation occurs through Strapi's plugin system. Many Strapi plugins expose their own authentication endpoints or rely on the main authentication system. For example, the Users & Permissions plugin's role-based access control can be bypassed if an attacker successfully stuffs credentials for a user with elevated permissions. The plugin architecture means that a single compromised account can potentially access multiple services within the Strapi ecosystem.

API endpoints that use Strapi's authentication middleware without additional protection are also vulnerable. Any endpoint using strapi.middleware.authenticate or similar authentication mechanisms becomes a potential target. Attackers can systematically test credentials across all protected endpoints, not just the login page, to find the path of least resistance. This is particularly problematic in Strapi applications that expose numerous authenticated endpoints for content management, user profiles, or administrative functions.

Detecting credential stuffing in Strapi requires monitoring authentication endpoint traffic patterns and analyzing login attempt characteristics. The first indicator is an unusual spike in authentication requests to /auth/local or /admin/auth/login. Strapi's default logging configuration records authentication attempts, but you need to actively monitor these logs for patterns like hundreds of failed attempts from the same IP address or geographically distributed IPs attempting logins in rapid succession.

MiddleBrick's API security scanner can detect credential stuffing vulnerabilities in Strapi installations by analyzing authentication endpoint configurations. The scanner tests for missing rate limiting on authentication endpoints, checks if detailed error responses reveal valid usernames, and verifies that authentication endpoints aren't exposed to unauthenticated users when they shouldn't be. MiddleBrick specifically looks for Strapi's default authentication patterns and identifies when these endpoints lack proper security controls.

Implement logging middleware in your Strapi application to track authentication attempts. Here's a Strapi-specific implementation:

const { Router } = require('@strapi/router');
const rateLimit = require('express-rate-limit');

// Create rate limiter for Strapi auth endpoints
const authLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 5, // limit each IP to 5 requests per windowMs
 req.ip
});

// Apply to Strapi's auth routes
strapi.app.use('/auth/local', authLimiter);
strapi.app.use('/admin/auth/login', authLimiter);

Monitor for specific attack signatures in your Strapi logs: multiple failed attempts with different passwords for the same username, rapid-fire requests from single or multiple IPs, and authentication attempts at unusual times. Strapi's default logging doesn't include detailed authentication analytics, so you'll need to implement custom monitoring or use security information and event management (SIEM) tools to correlate authentication events.

MiddleBrick's scanner can identify if your Strapi installation exposes authentication endpoints without proper security controls. The scanner tests for missing CAPTCHA on login forms, lack of IP-based blocking for repeated failures, and whether authentication endpoints return information that aids credential enumeration. For Strapi specifically, MiddleBrick checks the config/policies directory to see if authentication policies are properly configured and tests the actual runtime behavior of authentication endpoints.

Remediating credential stuffing in Strapi requires a multi-layered approach using Strapi's built-in features and external security controls. Start by implementing rate limiting at the Strapi application level using middleware. Strapi's plugin architecture allows you to create custom middleware that protects authentication endpoints:

// plugins/users-permissions/config/middleware.js
module.exports = ({ env }) => ({
  settings: {
    ratelimit: {
      enabled: true,
      driver: 'memory',
      store: {
        type: 'redis',
        host: env('REDIS_HOST', 'localhost'),
        port: env('REDIS_PORT', 6379),
        ttl: 3600
      }
    }
  }
});

Configure Strapi's built-in policies to protect authentication endpoints. In config/policies.js, add rate limiting and authentication policies:

module.exports = ({ env }) => ({
  ratelimit: {
    enabled: true,
    config: {
      windowMs: 900000, // 15 minutes
      max: 5, // 5 requests
      message: 'Too many login attempts'
    }
  },
  captcha: {
    enabled: true,
    secret: env('RECAPTCHA_SECRET')
  }
});

Implement CAPTCHA verification on authentication forms to prevent automated credential stuffing. Strapi supports reCAPTCHA integration through its plugin system:

// plugins/users-permissions/config/routes.json
[
  {
    "method": "POST",
    "path": "/auth/local",
    "handler": "AuthController.local",
    "config": {
      "policies": ["captcha", "ratelimit"]
    }
  }
]

Modify Strapi's error responses to prevent username enumeration. Create a custom authentication controller that returns generic error messages:

// api/auth/controllers/AuthController.js
const { sanitizeEntity } = require('strapi-utils');

module.exports = class AuthController extends strapi.BaseController {
  async local(ctx) {
    try {
      const { identifier, password } = ctx.request.body;
      const user = await strapi.query('user', 'users-permissions').findOne({
        $or: [{ email: identifier }, { username: identifier }]
      });

      if (!user) {
        // Always return same response regardless of whether user exists
        throw new Error('Invalid credentials');
      }

      return await strapi.plugins['users-permissions'].controllers.AuthController.local(ctx);
    } catch (error) {
      throw new strapi.errors.BadRequest(error.message);
    }
  }
};

Implement IP-based blocking for repeated authentication failures using Strapi's middleware system. Create a custom policy that tracks failed attempts and blocks suspicious IPs:

// api/policies/ip-blocker.js
const ipBlockList = new Set();
const failedAttempts = new Map();

module.exports = async (ctx, next) => {
  const ip = ctx.request.ip;
  
  if (ipBlockList.has(ip)) {
    ctx.response.status = 403;
    ctx.response.body = { message: 'Your IP has been temporarily blocked' };
    return;
  }
  
  await next();
  
  if (ctx.response.status === 401) {
    const attempts = failedAttempts.get(ip) || 0;
    failedAttempts.set(ip, attempts + 1);
    
    if (attempts > 10) {
      ipBlockList.add(ip);
      setTimeout(() => ipBlockList.delete(ip), 3600000); // block for 1 hour
    }
  }
};

Enable two-factor authentication (2FA) for all Strapi admin users through the Users & Permissions plugin. This adds an additional layer of protection even if credentials are compromised. Configure 2FA in plugins/users-permissions/config/jwt.js and require it for admin roles in your Strapi admin panel settings.