@joplin/onenote-converter: Path traversal in OneNote importer allows overwriting arbitrary files

### Summary A path traversal vulnerability in the OneNote importer allows overwriting arbitrary files on disk. ### Details The OneNote converter does not sanitize the names of embedded files before writing them to disk. As a result, it's possible for an attacker to create a malicious `.one` file that includes file names containing `../../`, that are then interpreted as part of the target path when extracting attachments from the `.one` file. One affected location is `embedded_file.rs`, which generates a file name from a string previously parsed from the `.one` file, https://github.com/laurent22/joplin/blob/af5108d70233b1db9410346958c1587cf7c1b16d/packages/onenote-converter/renderer/src/page/embedded_file.rs#L13-L16 Above, [`determine_filename`](https://github.com/laurent22/joplin/blob/af5108d70233b1db9410346958c1587cf7c1b16d/packages/onenote-converter/renderer/src/page/embedded_file.rs#L56-L64) passes through the provided file name. [Similar logic](https://github.com/laurent22/joplin/blob/4d7fa5972fe2986eae14cbf3a2801835cbe1384e/packages/onenote-converter/src/page/embedded_file.rs#L14) has been present since 4d7fa5972fe2986eae14cbf3a2801835cbe1384e (Joplin 3.2.2), when the OneNote importer was first introduced. ### PoC [Screencast from 2025-11-20 13-50-21.webm](https://github.com/user-attachments/assets/a9d6cc64-ec11-4f33-9f92-32efe0eaab23) 1. Import [poc_v2.zip](https://github.com/user-attachments/files/23664109/poc_v2.zip). 2. Open the application's profile directory, then open `log.txt`. 3. Observe that `log.txt` has been overwritten non-log-file content (a WAV file). Tested on Fedora Linux 43 with Joplin 3.4.12 (prod, linux) and Joplin 3.5.6 (dev, linux). **Note**: The PoC ZIP file overwrites Joplin's `log.txt`. It is also possible to craft a file that overwrites more sensitive system files (e.g. `.bashrc` on Linux). ### Impact This is a path traversal vulnerability that impacts **all versions of Joplin (<= v3.5.6) that include a OneNote importer**. Importing a crafted OneNote export file allows an attacker to overwrite arbitrary files, potentially leading to remote code execution. ### Patched in - **Joplin**: https://github.com/laurent22/joplin/commit/791668455e1aae50501ff57ea4783b3fba9d377c - **one2html**: https://github.com/msiemens/one2html/commit/948d65cdca5bb35d776b8b235ec05ff15249fd41