The exec_command function in common/helpers.py in Gajim before 0.15 allows user-assisted remote attackers to execute arbitrary commands via shell metacharacters in an href attribute.
https://trac.gajim.org/ticket/7031
http://www.securityfocus.com/bid/52943
http://www.openwall.com/lists/oss-security/2012/04/08/2
http://www.openwall.com/lists/oss-security/2012/04/08/1
http://security.gentoo.org/glsa/glsa-201208-04.xml