Ubuntu Security Notice USN-104-1 – Joey Hess discovered that unshar created temporary files in an insecure manner. This could allow a symbolic link attack to create or overwrite arbitrary files with the privileges of the user invoking the program.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/36974/USN-104-1.txt
Source: https://packetstormsecurity.com/files/36974/Ubuntu-Security-Notice-104-1.html