Credential Stuffing in Strapi with Bearer Tokens

Credential stuffing is an automated attack technique where previously breached username and password pairs are used to gain unauthorized access to accounts. In Strapi, if the application relies on Bearer Tokens for authentication without additional protections, credential stuffing can be particularly effective. Bearer Tokens are typically issued after a successful login and are then sent in the Authorization header as Authorization: Bearer <token>. If an attacker obtains a list of valid credentials and can repeatedly authenticate to obtain fresh tokens, or if tokens are long-lived and not bound to a strict scope or revocation mechanism, the API becomes vulnerable to unauthorized access via credential reuse.

Strapi’s default behavior may expose an unauthenticated attack surface when endpoints are not properly protected. For example, an endpoint like /api/users/me that returns user details based on a Bearer Token may not enforce strict rate limiting or anomaly detection. An attacker can automate requests using credential-stuffed token pairs, cycling through valid credentials to identify active sessions. Because Strapi’s permissions and roles are often tied to the authenticated identity, a successful credential stuffing attack can lead to privilege escalation if the attacker gains access to an account with higher privileges. Additionally, if Strapi’s API does not validate the token scope or enforce per-request token invalidation, reused tokens from prior breaches may remain valid for extended periods.

The combination of Strapi’s flexible authentication system and Bearer Token usage without multi-factor authentication or token binding increases risk. Attackers may leverage tools to test thousands of credential pairs against the Strapi authentication endpoint, extracting new tokens for each successful login. These tokens can then be used to probe other endpoints, such as content management APIs or user-specific data routes. Without proper monitoring or anomaly detection, such activity can persist undetected. The lack of mandatory token rotation or short-lived token policies further amplifies the impact of credential stuffing in this context.

Real-world attack patterns often involve using compromised credentials from breaches like those seen in the Collection #1–5 leaks. These credentials are tested against Strapi instances that expose authentication endpoints without adequate controls. The OWASP API Security Top 10 category ‘2023-A07: Identification and Authentication Failures’ directly applies here, as insufficient protection against automated credential validation undermines the integrity of the authentication mechanism. Strapi administrators must recognize that Bearer Tokens alone are insufficient without complementary defenses such as rate limiting, IP reputation checks, and token binding to mitigate credential stuffing risks.

To mitigate credential stuffing risks when using Bearer Tokens in Strapi, implement short-lived tokens, strict token validation, and binding mechanisms. Below are concrete remediation steps with code examples that can be applied within Strapi’s custom policies and configuration.

1. Enforce Short-Lived Tokens with Refresh Token Rotation

Ensure access tokens have a short time-to-live (TTL) and require refresh tokens for renewal. This limits the window of opportunity for reused credentials. In Strapi, you can customize the JWT configuration in ./config/jwt.js:

module.exports = {
  jwt: {
    secret: process.env.JWT_SECRET || 'your-secure-secret-key-change-in-production',
    expiresIn: '15m', // Short-lived access token
    refreshExpiresIn: '7d', // Refresh token with longer but bounded lifetime
    refreshSecret: process.env.REFRESH_JWT_SECRET || 'your-refresh-secret',
  },
};

This configuration ensures that even if a Bearer Token is compromised, it will expire quickly, reducing the impact of credential stuffing.

2. Implement Token Binding via Custom Policy

Bind tokens to client attributes such as IP address or user-agent to prevent token reuse across different contexts. Create a custom policy at ./api/permissions/policies/token-bind.js:

module.exports = {
  handler: async (ctx, next) => {
    const token = ctx.request.header.authorization?.split(' ')[1];
    if (!token) {
      return ctx.unauthorized('Token required');
    }

    try {
      const decoded = await strapi.plugins['users-permissions'].services.jwt.decode(token);
      const currentIp = ctx.request.ip;

      // Example: store and validate IP binding in session or cache
      const cachedIp = await strapi.cache.get(`token_ip:${decoded.sub}`);
      if (cachedIp && cachedIp !== currentIp) {
        return ctx.unauthorized('Token binding mismatch');
      }

      await strapi.cache.set(`token_ip:${decoded.sub}`, currentIp, { ttl: 900 });
      await next();
    } catch (err) {
      return ctx.unauthorized('Invalid token');
    }
  },
};

Apply this policy to sensitive routes to ensure tokens are not reused from different locations.

3. Rate Limit Authentication Endpoints

Prevent automated credential testing by applying rate limits to login and token issuance endpoints. Use Strapi’s built-in middlewares or integrate a rate-limiting plugin. Example using a custom middleware at ./src/middlewares/rate-limit-login.js:

const rateLimit = require('koa-rate-limit');

const loginLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 5, // Limit each IP to 5 login attempts per window
  message: 'Too many login attempts. Please try again later.',
  keyGenerator: (ctx) => ctx.request.ip,
});

module.exports = loginLimiter;

Then register this middleware in your Strapi middleware configuration to protect authentication routes.

4. Require Multi-Factor Authentication (MFA) for Sensitive Operations

For administrative endpoints or high-risk actions, enforce MFA even when a valid Bearer Token is present. This can be implemented via a custom policy that checks for MFA verification before allowing access:

module.exports = {
  handler: async (ctx, next) => {
    const user = ctx.state.user;
    if (user.role.type === 'admin' && !user.mfaVerified) {
      return ctx.forbidden('MFA required for admin actions');
    }
    await next();
  },
};

These remediation steps help ensure that Bearer Tokens in Strapi are used securely and are resilient against credential stuffing attacks.