Beast Attack in Strapi with Basic Auth

A Beast Attack (Branch Scope Enforcement Attack) in Strapi with Basic Auth can occur when authorization checks are performed after authentication but are dependent on data that is not bound to the authenticated identity. In Strapi, Basic Auth is typically enforced at the application layer or behind a reverse proxy, and once a user is authenticated, Strapi may use the user’s ID or role to fetch content. If those queries do not enforce record-level ownership as part of the same access check, an attacker can manipulate parameters such as IDs or ordering to leak data belonging to other users or tenants.

Consider an endpoint like /api/articles that supports filters such as userId. If the API first authenticates via Basic Auth (username and password) and then constructs a query like Article.find({ where: { userId: userIdFromToken } }) but the userId used in the filter is derived from request parameters instead of the authenticated identity, an attacker can change the parameter to enumerate other users’ articles. Because Basic Auth transmits credentials in each request, session fixation or credential reuse is not the primary concern; the risk is in how Strapi handles authorization after authentication.

In a typical Beast Attack flow with Basic Auth in Strapi:

• An attacker authenticates with a low-privilege Basic Auth credential.
• The attacker probes the same endpoint with manipulated identifiers (e.g., changing userId, categoryId, or foreign key references) or by leveraging ordering/pagination to trigger conditional branches that expose data or error messages.
• Because Strapi may not scope every query to the authenticated user’s tenant or enforce ownership on each model retrieval, the attacker can observe differences in response size, timing, or content, inferring the existence or absence of other records.

OpenAPI specs can inadvertently support this if paths define parameters that are not tied to the authenticated subject. For example, an parameters array including userId without requiring it to match the authenticated user enables the client-controlled branch. middleBrick’s OpenAPI/Swagger analysis resolves $ref definitions and cross-references these parameters with runtime behavior, helping to detect whether authorization is consistently bound to authentication.

Real-world attack patterns relevant here include IDOR when record-level constraints are missing and SSRF when internal endpoints are exposed through manipulated parameters. Although Strapi can hide internal services, an attacker may use SSRF to probe local metadata endpoints if input validation is weak. The LLM/AI Security checks in middleBrick test for system prompt leakage and prompt injection, which are unrelated to this Beast/IDOR scenario but illustrate how different attack classes are assessed independently.

Compliance mappings such as OWASP API Top 10 (2023) A01:2027 (Broken Object Level Authorization) align with this risk. middleBrick provides per-category breakdowns and prioritized findings with severity and remediation guidance, so teams can see exactly where authorization checks fail to bind data access to the authenticated identity.

To mitigate Beast Attacks when using Basic Auth in Strapi, ensure that every data retrieval is scoped to the authenticated subject and that parameters influencing branching are validated against the identity from the authentication layer. Do not rely solely on role or permission checks; enforce ownership or tenant scoping at the query level.

Example of insecure code that is vulnerable to Beast/IDOR:

// ❌ Insecure: userId from request query can be manipulated
module.exports = {
  async find(ctx) {
    const { userId } = ctx.query;
    const articles = await strapi.entityService.findMany('api::article.article', {
      filters: { userId },
    });
    return articles;
  },
};

Example of secure remediation that ties authorization to the authenticated identity:

// ✅ Secure: derive userId from the authenticated identity, ignore client-supplied userId
module.exports = {
  async find(ctx) {
    const { user } = ctx.state; // Assume Basic Auth sets user on state
    const articles = await strapi.entityService.findMany('api::article.article', {
      filters: { userId: user.id },
    });
    return articles;
  },
};

If you use Strapi’s authentication plugins with Basic Auth, extract the identity from the auth payload and use it to construct filters. Never pass user-controlled IDs directly into entity service queries without verifying that they belong to the authenticated subject.

For endpoints that must allow filtering, apply intersection checks. For example, if a client requests articles by a specific category, ensure the category belongs to the user’s organization or tenant:

// ✅ Secure with scoping: category must belong to the same user
module.exports = {
  async find(ctx) {
    const { user } = ctx.state;
    const { categoryId } = ctx.query;
    const category = await strapi.db.query('api::category.category').findOne({
      where: { id: categoryId, user: user.id },
    });
    if (!category) {
      return [];
    }
    const articles = await strapi.entityService.findMany('api::article.article', {
      filters: { categoryId: category.id },
    });
    return articles;
  },
};

middleBrick’s CLI tool (middlebrick scan <url>) can help detect whether responses vary based on manipulated identifiers, and the GitHub Action can integrate these checks into CI/CD pipelines to fail builds if risk scores drop below your threshold. The MCP Server allows you to run scans directly from your IDE while developing, reinforcing secure coding practices before deployment.