How to use URL query parameter on a View Exposed Filter?
Views Exposed filters already work this way, no need for any Contextual filters. 

In the settings for each Exposed filter there is an option to type in Filter identifier. That is the text that will be used for that field in the query. 

In your case set the Filter identifier of the Category to Category and of Type field to type. 



If you configure the Exposed filter Selection type settings for those two filters to Dropdown then you'll have to use term IDs in the link to make the filter work (I'm assuming your Security term has ID 6): 

www.mysite.com/news?Category=6

Use Autocomplete to get term names in query

But if you set the Exposed filter Selection type settings to Autocomplete you will be able to use term names, which is what you want. 

www.mysite.com/news?Category=Security 

or 

www.mysite.com/news?Category=Security+(6) 

Drupal 8 adds the term ID next to the term name when choosing from the autocomplete suggestion list, but that part isn't necessary. You can construct the link with Category name only and it will work. If the Category name has spaces in it, replace them with + in query. 

If you have more than one Exposed filter they get combined, for all types: 

www.mysite.com/news?Category=Chemistry

or 

www.mysite.com/news?Category=Chemistry&amp;type=

and for some specific type in addition to Category: 

www.mysite.com/news?Category=Chemistry&amp;type=Blog

or change order: 

www.mysite.com/news?type=Blog&amp;Category=Chemistry