Which method securely handles file uploads in JavaScript?
Secure file upload handling requires multiple checks: 1) Validate both MIME type and file content (don't trust just the extension), 2) Implement file size limits, 3) Scan for malware if possible, 4) Store files outside of public web root, 5) Generate new random filenames, 6) Validate file content matches declared type. Never rely solely on client-side validation.