ImpressCMS (www.impresscms.org) has published stable releases for both branches of ImpressCMS - the 1.2 LTS branch (for long term support) and the 1.3 branch - suitable for use on live sites.
Everyone is advised to update to one of these latest versions - they contain security updates that will protect your sites from malicious attacks.
Both releases provide updates to some of the external libraries used (jQuery, TCPDF, PHPMailer, PHPOpenID, just to name a few). They both also have improvements to consistently handling passwords and filtering user-supplied data. For a list of what has been updated, visit Assembla.com and review the milestone information for each - 1.2.7 Milestone and 1.3.1 Milestone
Several vulnerabilities were reported by High-Tech Bridge that existed in earlier versions of ImpressCMS. They have validated these releases remove those vulnerabilities.
Download 1.3.1 Final
Download 1.2.7 Final