Effectively, there is no inheritance performed on IPL Lists. When a process executes another executable the existing IPL Lists are simply overwritten. The reason for this design decision was that no examples requiring the feature were found and, more importantly, that the IPL inheritance would open the possibility of attacks on the IPL model. An example of possible attack scenario would be causing a mail client, which obviously needs to have permission to connect to local and/or destination MTA, to execute a script via buffer overflow or similar. This would cause the script to inherit the mail client's IPL Lists which is undesirable.