Next-Auth warning-issue

Question

I'm working on a Facebook clone code along. I am pretty new to Next.js

it throws an error at me which I'm not sure if it is standard or some bug in my code.

https://next-auth.js.org/warnings#no_secret
[next-auth][warn][NO_SECRET]

Can anyone explain it please ?

[...nextauth].js
import NextAuth from "next-auth"
import FacebookProvider from "next-auth/providers/facebook";

export default NextAuth({
    // Configure one or more authentication providers
    providers: [
        FacebookProvider({
            clientId: process.env.FACEBOOK_CLIENT_ID,
            clientSecret: process.env.FACEBOOK_CLIENT_SECRET
        })
    ]
})

import '../styles/globals.css'
import {SessionProvider} from "next-auth/react"

function MyApp({ Component, pageProps }) {
  return (
    <SessionProvider>
      <Component {...pageProps} />
    </SessionProvider>
  
  )}

export default MyApp

FACEBOOK_CLIENT_ID=495472355295570
FACEBOOK_CLIENT_SECRET=secret is from facebook for developers
NEXTAUTH_URL=http://localhost:3000```