GHSA-97wv-p4xx-c7mg - ApostropheCMS import-export tar guard misses './..' because it is a literal '../' substring test

### Summary The tar-extraction guard added to `@apostrophecms/import-export` for GHSA-mwxc-m426-3f78 is a literal substring test for `../`, and `./..` does not contain that substring. An entry named `./..` therefore passes the guard, `path.join` normalizes it to the parent of the export directory, and the resulting `fs.WriteStream` opens a directory and emits `EISDIR` with no `error` listener attached, which terminates the Node process. Confirmed on default-branch HEAD `1bd5d0a7a6fe880836fa75adad6964f1c577d640`, package version `3.6.2`. ### Details `packages/import-export/lib/formats/gzip.js`, in the tar-stream `entry` handler inside `extract(filepath, exportPath)`: ```js const name = header.name.replace(/\\/g, '/'); if (name.includes('../')) { // skipped } ... stream.pipe(fs.WriteStream(path.join(exportPath, name))); ``` Two separate problems sit in those four lines. The guard tests the raw entry name for a substring instead of resolving the joined path and requiring containment, and the write stream has no `error` handler, so any stream error becomes an unhandled `'error'` event. Reaching it needs an account that can import, nothing more. `packages/import-export/modules/@apostrophecms/import-export-page/index.js` exposes `post.importExportImport`, which calls into `lib/methods/import.js`; that handler requires `req.user` and then calls `format.input(exportPath)`, which for a `.gz` upload is `gzip.js` calling `extract()` on the uploaded archive. ### PoC This is not an end-to-end exploit. What follows is each of the three primitives the crash depends on, executed individually, plus a source-level trace of the route. The chain from `post.importExportImport` to `extract()` was read, not observed. The guard misses the payload: ```bash node -e "console.log('./..'.includes('../')); console.log('..'.includes('../')); console.log('a/./..'.includes('../'));" ``` ```text false false false ``` `path.join` then resolves it out of the export directory: ```bash n