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

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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.

Source published

15 Apr 2026 19:25:46 UTC

Source modified

15 Apr 2026 20:03:30 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

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.

Source published

Apr 15, 2026, 7:25:46 PM (timezone not stated)

Source modified

Apr 15, 2026, 8:03:30 PM (timezone not stated)

Observed here

1 Nov 2026 05:16:27 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

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.

Source published

15 Apr 2026 20:16:35 UTC

Source modified

26 Oct 2026 21:10:00 UTC

Observed here

27 Oct 2026 09:03:00 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

## 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`: ```javascript // 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: ```javascript // 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: ```javascript // 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: ```javascript // 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: ```bash 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: ```bash 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: ```bash 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 content, metadata, or other sensitive fields the administrator intentionally hid from the public API. - **Scope:** Affects all piece-type modules with `publicApiProjection` configured. The attacker cannot access documents they wouldn't otherwise be able to query (document-level permissions still apply), but they can read any field on accessible documents. - **Exploitability:** Trivial — requires only appending query parameters to a public URL. No authentication, special tools, or chaining required. ## Recommended Fix Remove the conditional check on `query.state.project` in `piece-type/index.js`, matching the page module's unconditional behavior. The admin-configured `publicApiProjection` should always override any user-supplied projection for unauthenticated users: ```javascript // modules/@apostrophecms/piece-type/index.js:1123-1134 // BEFORE (vulnerable): if (!omitPermissionCheck && !self.canAccessApi(req)) { if (!self.options.publicApiProjection) { query.and({ _id: null }); } else if (!query.state.project) { query.project({ ...self.options.publicApiProjection, cacheInvalidatedAt: 1 }); } } // AFTER (fixed): if (!omitPermissionCheck && !self.canAccessApi(req)) { if (!self.options.publicApiProjection) { query.and({ _id: null }); } else { query.project({ ...self.options.publicApiProjection, cacheInvalidatedAt: 1 }); } } ```

Source published

16 Apr 2026 20:42:21 UTC

Source modified

16 Apr 2026 21:11:29 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Publisher rating · MODERATE