It was found that xzgrep did not correctly process file names containing a semicolon. A local attacker able to trick a user to run xzgrep on a specially crafted file could use this flaw to execute arbitrary code as the user running xzgrep.
$ touch /tmp/semi\;colon $ xzgrep anystring /tmp/semi\;colon xz: /tmp/semi: No such file or directory /usr/bin/xzgrep: line 199: colon: command not found
Additional details:
http://seclists.org/oss-sec/2015/q2/484