python-filename-sanitization

Sanitizing user filenames in Python involves applying a whitelist-based regex to allow only safe characters while using pathlib to prevent directory traversal. This approach preserves file extensions and limits filename length for secure filesystem operations.

Directly using user input in Python file operations causes security issues because user filenames can contain malicious characters enabling path traversal, shell injection, or filesystem corruption during file uploads, renames, and downloads.

The best way to handle file uploads safely in Python web applications is to sanitize user-provided filenames before saving to disk. This uses a whitelist-based regex and pathlib to prevent unsafe filesystem operations and directory traversal.

Python pathlib prevents path traversal by avoiding shell commands during filesystem operations, but it must be paired with whitelist-based filename sanitization to filter malicious characters and safely handle user input across platforms and frameworks.

Yes, you can preserve file extensions when sanitizing filenames in Python. The whitelist-based sanitization process cleans the user-provided filename while explicitly retaining the original file extension for safe integration.