Can I read environment process variables of a react client in a browser?

Question

I'm currently doing a pentest for a client and I've come across something new to me. When I log in, I view the username/password values in burpsuite and find they are encrypted using Cryptojs. I'm looking at the debugger in the browser and come across this function:

  const encryptParams = parameters=> {
if (parameters) {
  return CryptoJs.AES.encrypt(parameters, process.env.REACT_APP_ENCRYPTION_KEY).toString();
} else {
  return null;
}

I can see that the encryption key is process.env.REACT_APP_ENCRYPTION_KEY, which with my little web development knowledge, is a value stored in a file using the dotenv module. Is there a way I can extract this value on the client side?

More info: I want to bruteforce the login, and I can't do it unless I encrypt the values so the backend can accept the POST request