CVE-2026-63667: ApostropheCMS: Arbitrary file read via import-export attachment-name path traversal

The @apostrophecms/import-export module reconstructs the on-disk source path of every imported attachment from JSON metadata contained in the uploaded archive.

The archive carries an aposAttachments.json file whose name and extension fields are concatenated into a filesystem path with no traversal check. The zip-slip guard that the module applies during tar extraction validates tar entry names only and does not cover this second path, which is built after extraction.

The file at the resulting path is read and copied into the public uploads directory, then served over HTTP without authentication. A ../ sequence in name makes the module read a file outside the extraction directory and publish it at an anonymous URL.

Result: an authenticated contributor reads any file on the host whose name ends in an allowlisted extension (other users’ uploaded documents, text or CSV dumps, PDFs) by importing a crafted archive and fetching the planted attachment anonymously.