Segurança de arquivos de upload do Laravel 5.1

php artisan make:request YourFormRequest

/**
 * Get the validation rules that apply to the request.
 *
 * @return array
 */
public function rules()
{
    return [
        'filename' => 'mimes:pdf,doc,jpeg,png,docx',
        // and other validation rules...
    ];
}

/**
 * Store the form values.
 * Don't forget to import the YourFormRequest class
 *
 * @param \App\Http\Requests\YourFormRequest $request
 * @return \Illuminate\Http\Redirect|string
 */
public function store(YourFormRequest $request)
{
    if($request->file('filename')) {
        $file = $request->file('filename');

        $fileName = $file->getClientOriginalName();
        $fileExt  = $file->getClientOriginalExtension();
        $fileMime = $file->getClientMimeType();

        // and rest of the file details

        // Move the file now
        $updatedFileName = $fileName.'.'.$fileExt;
        $file->move('path/to/destination/folder', $updatedFileName);

        // or using the Storage class, it is the same
        // as what you have written.
    }
}

/**
 * Authorize the request.
 *
 * @return bool
 */
public function authorize()
{
    return true; // replace false with true.
}