CVE-2026-33888: ApostropheCMS: publicApiProjection Bypass via `project` Query Builder in Piece-Type REST API

Vulnerability summary

CVE-2026-33888 is a medium (CVSS 5.3) vulnerability in apostrophecms apostrophe. EPSS estimates a 0.52% chance of exploitation in the next 30 days, higher than 43.3% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 15-04-2026
   PublishedVulnerability first disclosed.
2. 15-04-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-200Exposure of Sensitive Information to an Unauthorized ActorThe product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
• CWE-863Incorrect AuthorizationThe product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.