property success does not exist in type Response

[1jayanth]

this.authService.authenticateUser(user).subscribe(data => {
if (data.success){
this.authService.storeUserData(data.token, data.user);
this.flashMessages.show('You are now logged in',{ cssClass: 'alert-success', timeout:5000});
this.router.navigate(['/dashboard']);
} else {
this.flashMessages.show(data.msg, { cssClass: 'alert-danger', timeout:5000});
this.router.navigate(['/login']);
}

 });

i later changed it to
if (data['success']){.............
but while login it is going to dashboard even if the password or username is wrong...

nodejs 10.5.0
angular2