system: You are an expert security code reviewer. You will be shown a source code file along with a multiple-choice question listing several function or class names from that file. Your task is to identify which one contains the specified CWE vulnerability.

OUTPUT FORMAT: Respond with the single letter of the correct option, wrapped in \boxed{...}. Example: `\boxed{B}`. Output the boxed letter ONLY -- no explanation, no other text.

user: ```python
from flask import Flask, render_template, request, json, Response, redirect
from flask_sqlalchemy import SQLAlchemy
from werkzeug.utils import secure_filename
from errors import *
import os


app = Flask(__name__)
app.config.from_object(os.environ['APP_SETTINGS'])
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)


UPLOAD_FOLDER = 'static/images/headstone'
ALLOWED_IMAGE_EXTENSIONS = set(['jpg','gif','png'])
app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
ALLOWED_DATA_EXTENSIONS = set(['csv','zip'])

DOWNLOAD_FOLDER = 'static/download'
app.config['DOWNLOAD_FOLDER'] = DOWNLOAD_FOLDER


from models import Burial, BurialJSONEncoder, get_burials, get_burial, \
    add_burial, remove_all_burials, get_headstone, set_headstone, set_latlng


def allowed_image_file(filename):
    return '.' in filename and \
        filename.rsplit('.', 1)[1] in ALLOWED_IMAGE_EXTENSIONS


def allowed_data_file(filename):
    return '.' in filename and \
        filename.rsplit('.', 1)[1] in ALLOWED_DATA_EXTENSIONS


def split_csv_line(line):
    buf = ''
    cols = []
    in_quotes = False
    for i in range(0, len(line)):
        if line[i] == ',' and not in_quotes:
            cols.append(buf)
            buf = ''
        elif line[i] == '"':
            in_quotes = not in_quotes
        else:
            buf = buf + str(line[i])

    if buf == '\r':
        cols.append('')
    elif buf != '':
        cols.append(buf)

    # The CSV file may not have lat/lng values.
    # If not, give it defaults of 0,0.

    while len(cols) < 22:
        cols.append(0)

    return cols


@app.route('/')
def index():
    """Downloads the initial map page.
    """
    return render_template('index.html')


@app.route('/api/search', methods=['GET', 'POST'])
def search():
    """Returns a JSON list of matching burials.
    """
    try:
        js = json.dumps(get_burials(request.form), cls=BurialJSONEncoder)
        resp = Response(js, status=200, mimetype='application/json')
        return resp
    except Exception as e:
        return ERR_GENERAL


@app.route('/api/headstone/<int:id>', methods=['GET'])
def headstone_download(id):
    hsfilename = get_headstone(id)
    if hsfilename:
        return redirect( \
                os.path.join(app.config['UPLOAD_FOLDER'], hsfilename), \
                code=302)
    else:
        return redirect( \
                os.path.join(app.config['UPLOAD_FOLDER'], 'no-image.png'), \
                code=302)


@app.route('/api/headstone/<int:id>', methods=['POST'])
def headstone_upload(id):
    """Given an HTML form with enctype=multipart/form-data and an input
    type=file, this REST endpoint places a headstone image file into
    the upload folder UPLOAD_FOLDER and then updates the database
    with the new filename.
    """

    if not get_burial(id):
        return ERR_NO_SUCH_BURIAL

    try:
        if 'file' not in request.files:
            return ERR_NO_FILE_SPECIFIED
        file = request.files['file']
        if file.filename == '':
            return ERR_NO_FILE_SPECIFIED
        if file and allowed_image_file(file.filename):
            filename = secure_filename(file.filename)
            suffix = filename[filename.rindex('.'):]
            hsfilename = 'hs-' + str(id) + suffix
            filepath = os.path.join(app.config['UPLOAD_FOLDER'], hsfilename)
            file.save(filepath)
        else:
            return ERR_NOT_IMAGE
    except Exception as e:
        return ERR_GENERAL

    set_headstone(id, hsfilename)

    return 'ok'


@app.route('/api/data', methods=['GET'])
def database_download():
    """Retrieves a CSV file containing all database data.

    In a future version, this REST endpoint will retrieves a
    ZIP file containing a CSV of all database data
    and all headstone image files.
    """

    if not os.path.isdir(app.config['DOWNLOAD_FOLDER']):
        os.mkdir(app.config['DOWNLOAD_FOLDER'])

    from time import gmtime, strftime
    filename = 'cemdb-'+strftime('%Y%m%d-%H%M%S', gmtime())+'.csv'
    pathname = os.path.join(app.config['DOWNLOAD_FOLDER'], filename)

    with open(pathname, 'w') as csv_file:
        csv_file.write( \
            'id,sd_type,sd,lot,space,lot_owner,year_purch,first_name,' +
            'last_name,sex,birth_date,birth_place,death_date,age,' +
            'death_place,death_cause,burial_date,notes,more_notes,' +
            'hidden_notes,lat,lng\n' )

        burials = get_burials()

        for burial in burials:
            csv_file.write(str(burial.id)+',')
            csv_file.write('"'+burial.sd_type+'",')
            csv_file.write('"'+burial.sd+'",')
            csv_file.write('"'+burial.lot+'",')
            csv_file.write('"'+burial.space+'",')
            csv_file.write('"'+burial.lot_owner+'",')
            csv_file.write('"'+burial.year_purch+'",')
            csv_file.write('"'+burial.first_name+'",')
            csv_file.write('"'+burial.last_name+'",')
            csv_file.write('"'+burial.sex+'",')
            csv_file.write('"'+burial.birth_date+'",')
            csv_file.write('"'+burial.birth_place+'",')
            csv_file.write('"'+burial.death_date+'",')
            csv_file.write('"'+burial.age+'",')
            csv_file.write('"'+burial.death_place+'",')
            csv_file.write('"'+burial.death_cause+'",')
            csv_file.write('"'+burial.burial_date+'",')
            csv_file.write('"'+burial.notes+'",')
            csv_file.write('"'+burial.more_notes+'",')
            csv_file.write('"'+burial.hidden_notes+'",')
            csv_file.write(str(burial.lat)+',')
            csv_file.write(str(burial.lng)+'\n')

    return redirect(pathname, code=302)


@app.route('/api/data', methods=['POST'])
def database_upload():
    """Reloads all application data from a CSV file.

    In a future version, this REST endpoint will reload all
    # application data from a ZIP file containing
    a CSV of all database data and all headstone images.
    """

    if 'file' not in request.files:
        return ERR_NO_FILE_SPECIFIED
    file = request.files['file']
    if file.filename == '':
        return ERR_NO_FILE_SPECIFIED

    if file and allowed_data_file(file.filename):
        filename = secure_filename(file.filename)
        file.save(filename)

        remove_all_burials()

        import codecs
        with codecs.open(filename, 'r', encoding='utf-8', \
            errors='ignore') as csv_file:

            lines = csv_file.readlines()[1:]
            for line in lines:
                col_values = split_csv_line(line)
                add_burial( {
                    'sd_type' : col_values[1],
                    'sd' : col_values[2],
                    'lot' : col_values[3],
                    'space' : col_values[4],
                    'lot_owner' : col_values[5],
                    'year_purch' : col_values[6],
                    'first_name' : col_values[7],
                    'last_name' : col_values[8],
                    'sex' : col_values[9],
                    'birth_date' : col_values[10],
                    'birth_place' : col_values[11],
                    'death_date' : col_values[12],
                    'age' : col_values[13],
                    'death_place' : col_values[14],
                    'death_cause' : col_values[15],
                    'burial_date' : col_values[16],
                    'notes' : col_values[17],
                    'more_notes' : col_values[18],
                    'hidden_notes' : col_values[19],
                    'lat' : col_values[20],
                    'lng' : col_values[21],
                } )

    return 'ok - %d burials loaded' % len(lines)


@app.route('/api/burial-summary', methods=['GET'])
def burial_summary():
    """This REST endpoint is used by the Android camera app 'cemetery-cam'
    to retrieve a subset of burial information for all burials
    in the cemetery.  This subset is represented by a JSON array objects

        {
            id: ID,
            first_name: FNAME,
            last_name: LNAME,
            birth_date: BDATE,
            death_date : DDATE
        }

    where the CAPS strings represent the actual values returned.  Only actual
    burials are returned, not owned plots without an actual burial.  Callers
    can expect the burials to be alphabetized by last_name.

    This information is used by the camera app to select a burial prior to
    filling in its headstone photo and latitude/longitude.  The headstone photo
    and latitude/longitude get uploaded using the /api/update-burial REST URL.
    """
    try:
        burials = get_burials()
        burials_less = []
        for burial in burials:
            burials_less.append( {
                'id': burial.id,
                'first_name': burial.first_name,
                'last_name': burial.last_name,
                'birth_date': burial.birth_date,
                'death_date': burial.death_date,
            })

        burials_less = sorted( \
            list(filter(lambda b: b['last_name'] != "", burials_less)), \
            key=lambda b: b['last_name'])

        js = json.dumps(burials_less, cls=BurialJSONEncoder)
        resp = Response(js, status=200, mimetype='application/json')
        return resp
    except Exception as e:
        return ERR_GENERAL


@app.route('/api/update-burial', methods=['POST'])
def update_burial():
    """This REST endpoint is used by the Android camera app 'cemetery-cam'
    to update the latitude, longitude, and headstone image given a certain
    burial ID.
    """
    set_latlng(request.form['id'], request.form['lat'], request.form['lng'])
    headstone_upload(request.form['id'])
    return 'ok'


from models import make_dummy_data

@app.route('/api/add-test-latlng', methods=['GET', 'POST'])
def add_test_data():
    make_dummy_data()
    return 'ok'


if __name__ == '__main__':
    print('Using environment', os.environ['APP_SETTINGS'])
    app.run()

```

Which of the following functions or classes contains a `CWE-312: Cleartext Storage of Sensitive Information` vulnerability?

  A) database_download
  B) headstone_download
  C) index
  D) search
Answer: A