The notify function in pidgin-knotify.c in the pidgin-knotify plugin 0.2.1 and earlier for Pidgin allows remote attackers to execute arbitrary commands via shell metacharacters in a message.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.