== What is encoding?

Not trusting user input means validating data for type, length, format and range whenever it passes through a trust boundary,
say from a web form to an application script, and then encoding it prior to redisplay in a dynamic page.

In practice, this means that you need to review every point on your site where user-supplied data is handled and processed and
ensure that, before being passed back to the user, any values accepted from the client side are checked, filtered and encoded.

Client-side validation cannot be relied upon, but user input can be forced down to a minimal alphanumeric set with server-side
processing before being used by a web application in any way.

== Escaping

Escaping means that you convert (or mark) key characters of the data to prevent it from being interpreted in a dangerous context.
In the case of HTML output, you need to convert the < and > characters (among others), to prevent any malicious code from rendering.
Escaping these characters involves turning them into their entity equivalents \&lt; and \&gt;,
which will not be interpreted as HTML tags by a browser.

== Special characters

You need to encode special characters like "<" and ">" before they are redisplayed if they are received from user input.
For example, encoding "<" and ">" ensures a browser will display <script> but not execute it.
In conjunction to encoding, it is important that your web pages always define their character set so the browser will not interpret
special character encodings from other character sets.

Cross site scripting attacks usually occur when you manage to sneak a script (usually javascript) onto someone else's website, where
it can run maliciously.

=== Relevant XML/HTML special characters

|===
|Char |Escape string |
|<	|\&lt;|
|>	|\&gt;|
|"	|\&quot;|
|'	|\&#x27;|
|&	|\&amp;|
|/  |\&#x2F;|

|===




