Reword 5.6 strong parameters and private method stuff [ci skip]

guides/source/getting_started.md

@@ -749,10 +749,33 @@ article. Try it! You should get an error that looks like this:
 
 Rails has several security features that help you write secure applications,
 and you're running into one of them now. This one is called
-`strong_parameters`, which requires us to tell Rails exactly which parameters
-we want to accept in our controllers. In this case, we want to allow the
-`title` and `text` parameters, so add the new `article_params` method, and
-change your `create` controller action to use it, like this:
+`[strong_parameters](http://guides.rubyonrails.org/action_controller_overview.html#strong-parameters)`, 
+which requires us to tell Rails exactly which parameters are allowed into
+our controller actions.
+
+Why do you have to bother? The ability to grab and automatically assign
+all controller parameters to your model in one shot makes the programmer's 
+job easier, but this convenience also allows malicious use.  What if a 
+request to the server was crafted to look like a new article form submit 
+but also included extra fields with values that violated your applications 
+integrity? They would be 'mass assigned' into your model and then into the 
+database along with the good stuff - potentially breaking your application
+or worse.
+
+We have to whitelist our controller parameters to prevent wrongful 
+mass assignment.  In this case, we want to both allow and require the 
+`title` and `text` parameters for valid use of `create`.  The syntax for
+this introduces `require` and `permit`. The change will involve one line:
+
+```ruby
+  @article = Article.new(params.require(:article).permit(:title, :text))
+```
+
+This is often factored out into its own method so it can be reused by 
+multiple actions in the same controller, for example `create` and `update`.
+Above and beyond mass assignment issues, the method is often made 
+`private` to make sure it can't be called outside its intended context.  
+Here is the result:
 
 ```ruby
 def create
@@ -768,13 +791,7 @@ private
   end
 ```
 
-See the `permit`? It allows us to accept both `title` and `text` in this
-action.
-
-TIP: Note that `def article_params` is private. This new approach prevents an
-attacker from setting the model's attributes by manipulating the hash passed to
-the model.
-For more information, refer to
+TIP: For more information, refer to the reference above and 
 [this blog article about Strong Parameters](http://weblog.rubyonrails.org/2012/3/21/strong-parameters/).
 
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