Data Exposure in Strapi with Dynamodb

Strapi is an open-source headless CMS that allows custom database connectors. When configured to use Amazon DynamoDB as a data store, data exposure risks arise from mismatches between Strapi’s ORM-like expectations and DynamoDB’s attribute-based model. Data exposure in this context occurs when sensitive fields—such as internal identifiers, access tokens, or personally identifiable information (PII)—are returned to unauthenticated or low-privilege API consumers because authorization checks are bypassed or incomplete.

In a typical Strapi setup with a relational database, policies and middleware enforce ownership and role-based access before records are serialized and sent over HTTP. With DynamoDB, developers often map Strapi entities to DynamoDB tables where partition keys and sort keys replace traditional row IDs. If these mappings do not align with authorization logic—for example, if a query uses only a global secondary index without filtering by a user-owned partition key—an attacker may enumerate or retrieve records that should be isolated per tenant or per user.

Consider a user profile endpoint mapped to a DynamoDB table where userId is the partition key. If the Strapi controller exposes a /profiles/:id route that directly passes the id parameter as a DynamoDB Key without verifying that the authenticated user’s userId matches the requested key, an attacker can iterate through valid IDs and read other users’ profiles. This is a form of Insecure Direct Object Reference (IDOR) that is amplified by DynamoDB’s fast, index-based lookups and by Strapi’s default REST/GraphQL field exposure.

Additionally, DynamoDB’s sparse index behavior can unintentionally reveal data. Suppose a Strapi model includes a sensitive boolean field such as isReviewed that is used as a local secondary index attribute. If queries against this index do not include a filter on the partition key, or if the index projection includes sensitive attributes, an unauthenticated attacker leveraging open endpoints might infer the existence of specific records or extract metadata patterns. Data exposure also occurs when response serialization in Strapi includes fields that should be hidden based on permissions but are not filtered before being written to the DynamoDB item or returned in the HTTP response.

Real-world attack patterns mirror OWASP API Top 10 API1:2023 Broken Object Level Authorization and IDOR, with DynamoDB-specific concerns around key design and index usage. For example, a misconfigured GSI that includes sensitive attributes like email or role can become an unintended data channel. Compliance mappings such as GDPR Article 5(1)(f) and SOC 2 CC6.1 highlight the need for data minimization and strict access controls, which are undermined when DynamoDB queries return more data than necessary.

An example of insecure code is a Strapi controller that constructs a DynamoDB GetItem request using only the provided ID:

// Strapi controller (insecure)
const { DynamoDBClient, GetItemCommand } = require("@aws-sdk/client-dynamodb");
const client = new DynamoDBClient({ region: "us-east-1" });

module.exports = {
  async findOne(ctx) {
    const { id } = ctx.params;
    const command = new GetItemCommand({
      TableName: process.env.DYNAMODB_TABLE,
      Key: { id: { S: id } }
    });
    const response = await client.send(command);
    ctx.body = response.Item;
  }
};

If the API route is exposed without verifying that the authenticated user owns this id, any authenticated or unauthenticated caller who guesses or enumerates IDs can read arbitrary records. The fix requires tying the DynamoDB key to the authenticated user’s context and ensuring that Strapi’s policies enforce ownership before data is returned.

Remediation focuses on aligning DynamoDB access patterns with authorization boundaries and minimizing exposed data. Always enforce ownership checks at the data access layer by including the authenticated user’s identifier in the DynamoDB key condition. Use partition keys that incorporate tenant or user context, and avoid relying solely on client-supplied IDs.

First, design your DynamoDB table with a composite primary key that includes the user or tenant context. For example, use a PK (partition key) like USER#12345 and a SK (sort key) like PROFILE#metadata. This ensures that queries are scoped to a specific user or tenant, preventing cross-user reads even if an ID is guessed.

Second, apply attribute-level filters and projections to limit returned fields. DynamoDB’s ProjectionExpression and ExpressionAttributeNames help return only necessary attributes, reducing the impact of any residual exposure.

Below is a secure Strapi controller example that incorporates ownership verification and safe DynamoDB usage:

// Strapi controller (secure)
const { DynamoDBClient, GetItemCommand, QueryCommand } = require("@aws-sdk/client-dynamodb");
const client = new DynamoDBClient({ region: "us-east-1" });

async function getProfile(ctx) {
  const userId = ctx.state.user.id; // authenticated user ID from Strapi auth
  const { id } = ctx.params;

  // Ensure the requested profile belongs to the authenticated user
  if (!id || id !== userId) {
    ctx.status = 403;
    return { error: "Forbidden" };
  }

  const command = new GetItemCommand({
    TableName: process.env.DYNAMODB_TABLE,
    Key: {
      pk: { S: `USER#${userId}` },
      sk: { S: `PROFILE#${id}` }
    },
    // Limit returned attributes to reduce exposure
    ProjectionExpression: "id,name,emailVerified"
  });

  const response = await client.send(command);
  if (!response.Item) {
    ctx.status = 404;
    return { error: "Not found" };
  }

  // Map DynamoDB attribute values back to plain objects
  const item = response.Item;
  ctx.body = {
    id: item.id.S,
    name: item.name.S,
    emailVerified: item.emailVerified.BOOL
  };
}

module.exports = { getProfile };

For list endpoints that use a GSI, apply a key condition that includes the user partition key. For example, querying a USER#12345 partition key with a begins-with sort key ensures only that user’s items are returned:

// Strapi service (secure)
const { DynamoDBClient, QueryCommand } = require("@aws-sdk/client-dynamodb");
const client = new DynamoDBClient({ region: "us-east-1" });

async function listPosts(ctx) {
  const userId = ctx.state.user.id;
  const command = new QueryCommand({
    TableName: process.env.DYNAMODB_TABLE,
    IndexName: "UserIdIndex", // GSI with user as partition key
    KeyConditionExpression: "userId = :uid",
    ExpressionAttributeValues: {
      ":uid": { S: `USER#${userId}` }
    },
    ProjectionExpression: "postId,title,createdAt"
  });

  const response = await client.send(command);
  ctx.body = response.Items.map(item => ({
    postId: item.postId.S,
    title: item.title.S,
    createdAt: item.createdAt.S
  }));
}

module.exports = { listPosts };

Additional remediation steps include: - Enforce field-level permissions in Strapi policies to strip sensitive attributes before serialization. - Use DynamoDB fine-grained IAM policies to restrict actions per role, ensuring least privilege. - Audit index configurations to ensure sensitive attributes are not projected into GSIs used by unauthenticated endpoints. - Regularly review endpoint mappings between Strapi routes and DynamoDB key schemas to detect misalignments.