Add missing changelog entries from 2.1-stable
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 7fc5ee5..6192fec 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -241,7 +241,9 @@
 -  Fixed a bug - form_open() compared $action against site_url() instead of base_url().
 -  Fixed a bug - CI_Upload::_file_mime_type() could've failed if mime_content_type() is used for the detection and returns FALSE.
 -  Fixed a bug (#538) - Windows paths were ignored when using the :doc:`Image Manipulation Library <libraries/image_lib>` to create a new file.
--  Fixed a bug - When database caching was enabled, $this->db->query() checked the cache before binding variables which resulted in cached queries never being found
+-  Fixed a bug - When database caching was enabled, $this->db->query() checked the cache before binding variables which resulted in cached queries never being found.
+-  Fixed a bug - CSRF cookie value was allowed to be any (non-empty) string before being written to the output, making code injection a risk.
+-  Fixed a bug (#726) - PDO put a 'dbname' argument in it's connection string regardless of the database platform in use, which made it impossible to use SQLite.
 
 Version 2.1.0
 =============