CKEditor will change the opening bracket character < to the markup < and closing bracket character > to >. For example, if <input type="text"> is placed inside of a CKEditor code snippet, <input type="text"> will br produced. This will cause problems with CKEditor and the web page.
As an example, let's say you are using PHP to retrieve data from a column named content in a SQL database.
<?php $content = $row["content"]; ?>
The PHP htmlspecialchars function can be used to fix the problem where CKEditor changes certain special characters to HTML.
<?php $content = htmlspecialchars($row["content"], ENT_QUOTES); ?>