Rasa chatbot and cors locally throws an error in firefox console

Question

I created the bot locally by using rasa/rasa docker image and created flask application where I implemented code form the docs https://rasa.com/docs/rasa/connectors/your-own-website/

But when I run flask server I can see the widget and when I start conversation, in firefox console I get the error "Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8080/socket.io/?EIO=4&transport=polling&t=N_GKcL4. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 404."

My credentials.yml is:

# This file contains the credentials for the voice & chat platforms
# which your bot is using.
# https://rasa.com/docs/rasa/messaging-and-voice-channels

rest:
#  # you don't need to provide anything here - this channel doesn't
#  # require any credentials


#facebook:
#  verify: "<verify>"
#  secret: "<your secret>"
#  page-access-token: "<your page access token>"

#slack:
#  slack_token: "<your slack token>"
#  slack_channel: "<the slack channel>"
#  slack_signing_secret: "<your slack signing secret>"

socketio:
  user_message_evt: user_uttered
  bot_message_evt: bot_uttered
  session_persistence: false

#mattermost:
#  url: "https://<mattermost instance>/api/v4"
#  token: "<bot token>"
#  webhook_url: "<callback URL>"

# This entry is needed if you are using Rasa X. The entry represents credentials
# for the Rasa X "channel", i.e. Talk to your bot and Share with guest testers.
rasa:
  url: "http://localhost:5002/api"

My flask code is

<h1>This is home</h1>
<div id="rasa-chat-widget" data-websocket-url="http://localhost:8080/socket.io"></div>
<script src="https://unpkg.com/@rasahq/rasa-chat" type="application/javascript"></script>

Why am I getting this error in firefox console and how to fix it?