Fix #346

When ['global_xss_filtering'] was turned on, the , ,  &
superglobals were automatically overwritten. This resulted in one of the following problems:

 - xss_clean() being called twice
 - Inability to retrieve the original (not filtered) value

XSS filtering is now only applied on demand by the Input class, and the default value for
the  parameter in CI_Input methods is changed to NULL. Unless a boolean value is
passed to them, whether XSS filtering is applied depends on the ['global_xss_filtering']
value.

1 files changed, 38 insertions, 7 deletions

diff --git a/user_guide_src/source/installation/upgrade_300.rst b/user_guide_src/source/installation/upgrade_300.rst
index 41153df16..f0759a15e 100644
--- a/user_guide_src/source/installation/upgrade_300.rst
+++ b/user_guide_src/source/installation/upgrade_300.rst
@@ -188,8 +188,39 @@ Many methods and functions now return NULL instead of FALSE when the required it
    - element()
    - elements()
 
+*******************************
+Step 11: Usage of XSS filtering
+*******************************
+
+Many functions in CodeIgniter allow you to use its XSS filtering feature
+on demand by passing a boolean parameter. The default value of that
+parameter used to be boolean FALSE, but it is now changed to NULL and it
+will be dynamically determined by your ``$config['global_xss_filtering']``
+value.
+
+If you used to manually pass a boolean value for the ``$xss_filter``
+parameter or if you've always had ``$config['global_xss_filtering']`` set
+to FALSE, then this change doesn't concern you.
+
+Otherwise however, please review your usage of the following functions:
+
+ - :doc:`Input Library <../libraries/input>`
+
+   - input->get()
+   - input->post()
+   - input->get_post()
+   - input->cookie()
+   - input->server()
+   - input->input_stream()
+
+ - :doc:`Cookie Helper <../helpers/cookie_helper>` :func:`get_cookie()`
+
+.. important:: Another related change is that the ``$_GET``, ``$_POST``,
+	``$_COOKIE`` and ``$_SERVER`` superglobals are no longer
+	automatically overwritten when global XSS filtering is turned on.
+
 ********************************************************
-Step 11: Update usage of Input Class's get_post() method
+Step 12: Update usage of Input Class's get_post() method
 ********************************************************
 
 Previously, the :doc:`Input Class <../libraries/input>` method ``get_post()``
@@ -200,14 +231,14 @@ A method has been added, ``post_get()``, which searches in POST then in GET, as
 ``get_post()`` was doing before.
 
 ***********************************************************************
-Step 12: Update usage of Directory Helper's directory_map() function
+Step 13: Update usage of Directory Helper's directory_map() function
 ***********************************************************************
 
 In the resulting array, directories now end with a trailing directory
 separator (i.e. a slash, usually).
 
 *************************************************************
-Step 13: Update usage of Database Forge's drop_table() method
+Step 14: Update usage of Database Forge's drop_table() method
 *************************************************************
 
 Up until now, ``drop_table()`` added an IF EXISTS clause by default or it didn't work
@@ -229,7 +260,7 @@ If your application relies on IF EXISTS, you'll have to change its usage.
 	all drivers with the exception of ODBC.
 
 ***********************************************************
-Step 14: Change usage of Email library with multiple emails
+Step 15: Change usage of Email library with multiple emails
 ***********************************************************
 
 The :doc:`Email Library <../libraries/email>` will automatically clear the
@@ -244,7 +275,7 @@ pass FALSE as the first parameter in the ``send()`` method:
  	}
 
 ***************************************************
-Step 15: Update your Form_validation language lines
+Step 16: Update your Form_validation language lines
 ***************************************************
 
 Two improvements have been made to the :doc:`Form Validation Library
@@ -275,7 +306,7 @@ files and error messages format:
 	later.
 
 ****************************************************************
-Step 16: Remove usage of (previously) deprecated functionalities
+Step 17: Remove usage of (previously) deprecated functionalities
 ****************************************************************
 
 In addition to the ``$autoload['core']`` configuration setting, there's a
@@ -491,7 +522,7 @@ CodeIgniter 3.1+.
 	sooner rather than later.
 
 ***********************************************************
-Step 17: Check your usage of Text helper highlight_phrase()
+Step 18: Check your usage of Text helper highlight_phrase()
 ***********************************************************
 
 The default HTML tag used by :doc:`Text Helper <../helpers/text_helper>` function