GHSA-c276-fj82-f2pq: ApostropheCMS: Information Disclosure via choices/counts Query Parameters Bypassing publicApiProjection Field Restrictions
SummaryThe `choices` and `counts` query parameters in the Apostrophe CMS REST API allow unauthenticated users to extract distinct field values for any schema field that has a registered query builder, completely bypassing `publicApiProjection` restrictions that are intended to limit which fields are exposed publicly. Fields protected by `viewPermission` are similarly exposed.DetailsWhen a piece type configures `publicApiProjection` to enable public API access while restricting visible fields, the restriction is enforced via a MongoDB projection on the main query (piece-type/index.js:1130-1134). However, the `choices` and `counts` query builders bypass this protection through a separate code path.The vulnerable flow:`getRestQuery` at piece-type/index.js:1120 calls `applyBuildersSafely(req.query)` (line 1122), which processes query parameters including `choices` and `counts` since both have `launder` methods (doc-type/index.js:2627-2628 and 2675-2676).The `publicApiProjection` is applied afterward (line 1130-1134) as a MongoDB projection on the main query.During query execution, the `choices` builder's `after` handler (doc-type/index.js:2636-2668) iterates over requested field names. The only validation is:The field has a registered builder (`_.has(query.builders, filter)` at line 2651)The builder has a `launder` method (line 2656)All schema field types (string, integer, float, select, boolean, date, slug, relationship) register query builders with `launder` methods via `addQueryBuilder` in `addFieldTypes.js`.`toChoices` (line 2661) calls the field's `choices` function, which typically calls `sortedDistinct` → `toDistinct`. The `toDistinct` method (doc-type/index.js:2811) executes `db.distinct(property, criteria)` — a MongoDB operation that returns all distinct values for the given property matching the criteria. **MongoDB's `distinct` operation does not respect projections**; it operates directly on the specified field regardless of any projection set on the query.The results are stored via `query.set('choicesResults', choices)` (line 2666) and returned directly in the API response at piece-type/index.js:292-296 without any filtering against `publicApiProjection` or `removeForbiddenFields`.The same bypass applies to `viewPermission`-protected fields: `removeForbiddenFields` (doc-type/index.js:1585-1611) only processes document results from `toArray()`, not the separate choices/counts data.The page REST API has the same issue at page/index.js:371-376.PoCImpact**Distinct field values leaked**: An unauthenticated attacker can extract all distinct values of any schema field on any piece type that has `publicApiProjection` configured, even when those fields are explicitly excluded from the projection.**Field types affected**: All field types that register query builders: string, slug, integer, float, select, boolean, date, and relationship fields.**Count disclosure**: The `counts` variant additionally reveals how many documents have each distinct value, providing statistical information about the dataset.**viewPermission bypass**: Fields protected with `viewPermission` (intended for role-based field access) are also exposed via this path.**Both APIs affected**: The piece-type REST API (piece-type/index.js:292-296) and page REST API (page/index.js:371-376) are both vulnerable.**Real-world impact**: If a CMS stores sensitive data in schema fields (e.g., internal status values, priority levels, internal categories, user-facing content marked as restricted), all distinct values are extractable by any unauthenticated visitor.Recommended FixIn the `choices` builder's `after` handler (doc-type/index.js:2636-2668), add validation to skip fields not permitted by `publicApiProjection` and `viewPermission`:Additionally, apply the same fix in the page REST API handler (page/index.js) for consistency.
CVSS v3.1: 5.3