Drupal 8.x

I am developing a custom module in Drupal8. This is my first attempt at module development. Earlier i had some custom php code in the Page itself. 

In Drupal 8 , the PHP format is removed (or not recommended) , i am developing a custom module. 

My module is a form with bunch of fields (textfield, drop down and checkboxes) . 

On submit , i need to go to a Display Page with the results (after some calculation based on the entered fields ) . 

Hello,

I ran a vulnerability scan on my site this evening. Everything all good apart from a couple of warnings. Is this something that I should address? I think these cookies are set via core but if someone could offer some insight/solution that'd be great. Thanks.

Insecure cookie setting: missing HttpOnly flag
/big_pipe/no-js?destination=/en/user/password
Set-Cookie: big_pipe_nojs

Currently I can only set the text filter to allow or prohibit images from remote sources. Means I can either stop all such images or I have to allow all such images.

Is there any way to override this? Say I want to allow from a known host and prohibit from others.

I was hoping "hook_filter_secure_image_alter" from filter module could be used to do this; however did not get any examples on how to exactly do that. (Or even whether such a possibility exists)

Will it require me to extend/override any class?

Please help.

Thanks

I have a views tpl where I set a variable but nomatter what I do, I can't get the output as a string ... even-though the drupal dump is indicating the value is set before AND after the output.

{% set foo = 'bar' %}
{{ dd(foo) }}
{{ foo }}
{{ dd(foo) }}

Hello,

I have just installed the Simplenews subscription module on Drupal 8. I have activated the module but it shows "First Name" and "Last Name" along with "Email" field. I want to remove the fields, but unable to find them. After spending most 8 hours, I could not find. it. google was not help at all.

Please help.