ApostropheCMS import-export: NoSQL injection via update-key value lets a crafted import match and overwrite an unidentified document

Summary

@apostrophecms/import-export's update-by-key feature lets an imported document carry a <field>:key property (for example slug:key) whose value is used to find an existing document to update instead of inserting a new one. getUpdateKey()/insertOrUpdateDocWithKey() (lib/methods/import.js) use that value directly as a MongoDB query value with no laundering:

const matchingDraftPromise = manager.findForEditing(
  req.clone({ mode: 'draft' }),
  {
    aposMode: 'draft',
    [updateField]: doc[updateKey]
  }).toObject();

Archive documents are parsed with EJSON (see lib/formats/gzip.js), which revives objects such as { $ne: null } as live values, the same untrusted data source and revival mechanism already fixed once in this module for findSingletonAposDocId/findParkedAposDocId in GHSA-79qf-vqgc-7xx3. That fix did not touch insertOrUpdateDocWithKey, so the identical class of bug survives here: a crafted "slug:key": { "$ne": null } entry in an archive's aposDocs.json makes the import match (and then update) an existing document the archive's author never actually identified, instead of failing to find a match.

Impact

Reaching this requires only an authenticated session with import access to the target type (the built-in contributor role holds this, matching the precondition of GHSA-79qf-vqgc-7xx3), and no admin interaction. Because the match uses a MongoDB operator instead of an exact value, it is not limited to a document the importer already knows the identifying field of: any existing document the importer has generic edit rights on and that satisfies the operator (which { $ne: null } trivially does for any doc with a non-null value in that field) is a candidate, and Apostrophe's findForEditing permission filter, not the update-key logic, is the only thing narrowing which document actually gets matched and overwritten.

Live-verified: a contributor-role request importing a document containing "slug:key": { "$ne": null } had its content applied to an existing, unrelated draft article, overwriting its title, while the importer never specified that article's real slug.

Affected versions

Confirmed on main branch HEAD as of 2026-09-04, packages/import-export/lib/methods/import.js.

Suggested fix

Launder doc[updateKey] to a plain string (mirroring the fix already applied to type/aposLocale/ in GHSA-79qf-vqgc-7xx3) before using it as a query value, and fall back to the insert path when it is not a usable string.