If you want use Captcha, you must set these values in freecap.php if they differ from default values or your config settings,
so that Captcha can pass its values to the session. This is a workaround until a more general approach is found / implemented.

1. $this->config['cookie_prefix'] can be access via the Admin panel or phpMyAdmin and config table.
2. -
3. The session handler path can be determined with ini_get('session.save_path') or via phpinfo(); and session.save_path.
   1. You can also look up the value via Admin panel and System Informations.
   2. If you specify the SESSION_HANDLER_PATH then this must be done in in both files.
   3. If the path containing additional values like '3;600;/home/web-sessions' then add the entire string.
   4. In some cases the SESSION_HANDLER_PATH must be provided in any case to get it work.

Example

table prefix_config

config/constants.php

define('SESSION_HANDLER_ID',			'sid');
define('SESSION_HANDLER_PATH',			null);	// if you are using specific path (instead of system default /tmp) for session variables storing, define it here	

lib/captcha/freecap.php

define('COOKIE_PREFIX',            'wacko_');         // Part 1 of session_name - see init.php session function for details "  session_name($this->config['cookie_prefix'].SESSION_HANDLER_ID);  "
define('SESSION_HANDLER_ID',            'sid');       // Part 2 of session_name - see previous . Same setting as in config/constants.php
define('SESSION_HANDLER_PATH',            null);    // Where to find session files. Same setting as in config/constants.php	

$catch_session_name = COOKIE_PREFIX.SESSION_HANDLER_ID;

if(isset($_GET[$catch_session_name]))
{
	session_name($catch_session_name);
	session_id($_GET[$catch_session_name]);

	// Save session information where specified or with PHP's default
	session_save_path(SESSION_HANDLER_PATH);

	session_start();	// we don't actually start a new session - we open the existing one by name & id and add our variables
}