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
"""Mailer script."""

import hashlib
import sys
import os
import smtplib
import urllib2
from urlparse import urlparse
from optparse import OptionParser
from flask import Flask, request, redirect, url_for, render_template, session
from email.MIMEMultipart import MIMEMultipart
from email.MIMEBase import MIMEBase
from email import encoders
import time
import datetime



reload(sys)
sys.setdefaultencoding("utf-8")

app = Flask(__name__)
app.secret_key = hashlib.sha1(os.urandom(128)).hexdigest()


@app.route("/", methods=['GET', 'POST'])
def index():
    """Function that handles the Email form."""
    if request.method == 'POST':
        email = request.form['email']
        file_url = request.form['file_url']
        file_name = request.form['file_name']
        mailer(email, file_url, file_name)
        session["data"] = email
        return redirect(url_for('submit'))
    return render_template('index.html')


@app.route("/submit", methods=['GET'])
def submit():
    """Function that redirects to success page."""
    return render_template('submit.html', data=session["data"])


def mailer(email, file_url, file_name):
    """Function that downloads and emails the file."""

    ts = time.time()
    timestamp = datetime.datetime.fromtimestamp(ts).strftime('%Y-%m-%d-%H-%M-%S')


    fromaddr = "freetamilebooksteam@gmail.com"
    toaddr = email
    password = "password here "
    msg = MIMEMultipart()
    msg["Subject"] = "Ebook from FreeTamilEbooks.com"
    msg['From'] = fromaddr
    msg['To'] = toaddr
#    msg['cc'] = "tshrinivasan@gmail.com"
    part = MIMEBase('application', 'octet-stream')
    parsed_uri = urlparse(file_url)
    if parsed_uri.hostname == 'freetamilebooks.com':	
        
        req = urllib2.Request(
        file_url,
        headers={
            'User-Agent':
            'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11'
        })

#    file_name = file_name.encode('utf-8')

#    file_name = "/tmp/" + timestamp + "-" + file_name
#    print file_name
#    os.system(" wget -O " + file_name + "   "  + file_url)

        part.set_payload(urllib2.urlopen(req).read())
#    part.set_payload(open(file_name).read())
        encoders.encode_base64(part)
        part.add_header('Content-Disposition',
#                    "attachment; filename= %s" % os.path.basename(file_name))
                     "attachment; filename= %s" % file_name)
        msg.attach(part)
        server = smtplib.SMTP('smtp.gmail.com', 587)
        server.ehlo()
        server.starttls()
        server.ehlo() 
        server.login(fromaddr, password)
        text = msg.as_string()
        server.sendmail(fromaddr, toaddr, text)
        server.quit()

        log = open("/var/www/html/Send2Kindle/logs/log.csv", "a")
        log_content = timestamp +"," + email + "," + file_url +"," + file_name + "\n"
        log.write(log_content)
        log.close()

if __name__ == "__main__":
    parser = OptionParser()
    parser.add_option(
        "-p",
        "--port",
        dest="port",
        help="Port on which the app will run",
        default=5000)
    (options, args) = parser.parse_args()
    app.run(host='0.0.0.0', debug=True, port=int(options.port))

```

Which of the following functions or classes contains a `CWE-918: Server-Side Request Forgery (SSRF)` vulnerability?

  A) submit
  B) index
  C) mailer
Answer: C