diff --git a/system/libraries/Session.php b/system/libraries/Session.php
index 2cdd50c..afa4334 100644
--- a/system/libraries/Session.php
+++ b/system/libraries/Session.php
@@ -196,7 +196,22 @@
 		{
 			$session = $this->CI->encrypt->decode($session);
 		}
+		else
+		{	
+			// encryption was not used, so we need to check the md5 hash
+			$hash = substr($session, strlen($session)-32); // get last 32 chars
+			$session = substr($session, 0, strlen($session)-32);
 
+			// Does the md5 hash match?  This is to prevent manipulation of session data
+			// in userspace
+			if ($hash !==  md5($session.$this->CI->config->item('encryption_key')))
+			{
+				log_message('error', 'The session cookie data did not match what was expected. This could be a possible hacking attempt.');
+				$this->sess_destroy();
+				return FALSE;
+			}
+		}
+		
 		$session = @unserialize($this->strip_slashes($session));
 		
 		if ( ! is_array($session) OR ! isset($session['last_activity']))
@@ -284,6 +299,11 @@
 		{
 			$cookie_data = $this->CI->encrypt->encode($cookie_data);
 		}
+		else
+		{
+			// if encryption is not used, we provide an md5 hash to prevent userside tampering
+			$cookie_data = $cookie_data . md5($cookie_data.$this->CI->config->item('encryption_key'));
+		}
 
 		setcookie(
 					$this->sess_cookie,
diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index d90f79a..b0fa83d 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -68,6 +68,7 @@
 	<li>Libraries
 		<ul>
 			<li>Added increased security for filename handling in the Upload library.</li>
+			<li>Added increased security for sessions for client-side tampering.</li>
 		</ul>
 	</li>
     <li>Helpers
diff --git a/user_guide/installation/index.html b/user_guide/installation/index.html
index 336f758..e925c21 100644
--- a/user_guide/installation/index.html
+++ b/user_guide/installation/index.html
@@ -62,7 +62,7 @@
 <ol>
 <li>Unzip the package.</li>
 <li>Upload the CodeIgniter folders and files to your server.  Normally the index.php file will be at your root.</li>
-<li>Open the <dfn>application/config/config.php</dfn> file with a text editor and set your base URL.</li>
+<li>Open the <dfn>application/config/config.php</dfn> file with a text editor and set your base URL.  If you intend to use encryption or sessions, set your encryption key.</li>
 <li>If you intend to use a database, open the <dfn>application/config/database.php</dfn> file with a text editor and set your database settings.</li>
 </ol>
 
diff --git a/user_guide/installation/upgrade_162.html b/user_guide/installation/upgrade_162.html
new file mode 100644
index 0000000..7fd01ea
--- /dev/null
+++ b/user_guide/installation/upgrade_162.html
@@ -0,0 +1,103 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
+<head>
+
+<title>CodeIgniter User Guide : Upgrading from 1.6.1 to 1.6.2</title>
+
+<style type='text/css' media='all'>@import url('../userguide.css');</style>
+<link rel='stylesheet' type='text/css' media='all' href='../userguide.css' />
+
+<script type="text/javascript" src="../nav/nav.js"></script>
+<script type="text/javascript" src="../nav/prototype.lite.js"></script>
+<script type="text/javascript" src="../nav/moo.fx.js"></script>
+<script type="text/javascript" src="../nav/user_guide_menu.js"></script>
+
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<meta http-equiv='expires' content='-1' />
+<meta http-equiv= 'pragma' content='no-cache' />
+<meta name='robots' content='all' />
+<meta name='author' content='ExpressionEngine Dev Team' />
+<meta name='description' content='CodeIgniter User Guide' />
+
+</head>
+<body>
+
+<!-- START NAVIGATION -->
+<div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('../');</script></div></div>
+<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="../images/nav_toggle.jpg" width="153" height="44" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
+<div id="masthead">
+<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
+<tr>
+<td><h1>CodeIgniter User Guide Version 1.6.1</h1></td>
+<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
+</tr>
+</table>
+</div>
+<!-- END NAVIGATION -->
+
+
+<!-- START BREADCRUMB -->
+<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
+<tr>
+<td id="breadcrumb">
+<a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
+<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;
+Upgrading from 1.6.0 to 1.6.1
+</td>
+<td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="codeigniter.com/user_guide/" />Search User Guide&nbsp; <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" />&nbsp;<input type="submit" class="submit" name="sa" value="Go" /></form></td>
+</tr>
+</table>
+<!-- END BREADCRUMB -->
+
+<br clear="all" />
+
+
+<!-- START CONTENT -->
+<div id="content">
+
+<h1>Upgrading from 1.6.1 to 1.6.2</h1>
+
+<p>Before performing an update you should take your site offline by replacing the index.php file with a static one.</p>
+
+
+
+<h2>Step 1: Update your CodeIgniter files</h2>
+
+<p>Replace these files and directories in your "system" folder with the new versions:</p>
+
+<ul>
+
+<li><dfn>system/codeigniter</dfn></li>
+<li><dfn>system/database</dfn></li>
+<li><dfn>system/helpers</dfn></li>
+<li><dfn>system/language</dfn></li>
+<li><dfn>system/libraries</dfn></li>
+</ul>
+
+<p class="important"><strong>Note:</strong> If you have any custom developed files in these folders please make copies of them first.</p>
+
+
+<h2>Step 2: Encryption Key</h2>
+<p>If you are using sessions, open up system/application/config.php and verify you've set an encryption key.</p>
+
+
+<h2>Step 3: Update your user guide</h2>
+<p>Please also replace your local copy of the user guide with the new version.</p>
+
+</div>
+<!-- END CONTENT -->
+
+
+<div id="footer">
+<p>
+Previous Topic:&nbsp;&nbsp;<a href="index.html">Installation Instructions</a>
+&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
+<a href="#top">Top of Page</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
+<a href="../index.html">User Guide Home</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
+Next Topic:&nbsp;&nbsp;<a href="../overview/at_a_glance.html">CodeIgniter at a Glance</a>
+</p>
+<p><a href="http://codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2006-2008 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">Ellislab, Inc.</a></p>
+</div>
+
+</body>
+</html>
\ No newline at end of file