Cleartext Transmission of Sensitive Information
Joomla! 1.5.8 does not set the secure flag for the session cookie in an https session, which makes it easier for remote attackers to capture this cookie by intercepting its transmission within an http session.
CWE-319 - Cleartext Transmission of Sensitive Information
The software transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.