Cisco Jabber 10.6.x, 11.0.x, and 11.1.x on Windows allows man-in-the-middle attackers to conduct STARTTLS downgrade attacks and trigger cleartext XMPP sessions via unspecified vectors, aka Bug ID CSCuw87419.
http://www.synacktiv.com/ressources/cisco_jabber_starttls_downgrade.pdf
http://www.securitytracker.com/id/1034540
http://www.securityfocus.com/bid/79678
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151224-jab