5432 port in iptables

I have opened the 5432 port in my iptables. Is there any info
on the security implications of this?

I have also set up a script run by fax; the
script runs when a fax is received; it sets the
java environment and runs a java program to load
the fax to postgresql.

The java script is run by a bin process; have I done a bad thing
for security by setting the script classpath?

TIA
rfjones