How do you handle file uploads in a Flask application?
Instruction: Explain the process and considerations for handling file uploads in Flask.
Context: This question examines the candidate's ability to implement file upload functionality, including security and file management considerations.
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Accept uploads through a multipart request and read the expected entry from request.files. Distinguish a missing field, empty filename, unsupported content and a size-limit failure so users receive useful errors.
Treat both the supplied filename and declared Content-Type as untrusted. Extension and MIME allowlists are preliminary checks, not proof of content safety. Parse or inspect allowed formats with maintained tools under resource limits, and apply malware/quarantine policy appropriate to the product before making content available...