ApostropheCMS is an open-source content management framework. Prior to version 3.5.3 of "@apostrophecms/import-export", The "extract()" function in "gzip.js" constructs file-write paths using "fs.createWriteStream(path.join(exportPath, header.name))". "path.join()" does not resolve or sanitise traversal segments such as "../". It concatenates them as-is, meaning a tar entry named "../../evil.js" resolves to a path outside the intended extraction directory. No canonical-path check is performed before the write stream is opened. This is a textbook Zip Slip vulnerability. Any user who has been granted the Global Content Modify permission — a role routinely assigned to content editors and site managers — can upload a crafted ".tar.gz" file through the standard CMS import UI and write attacker-controlled content to any path the Node.js process can reach on the host filesystem. Version 3.5.3 of "@apostrophecms/import-export" fixes the issue.