Hi,
The "Itemid" come from Joomla itself and there is no vulnerability in that parameter which just accept a number.
So, there is nothing to do ; except generating some URL with valid itemid so the url will be right SEF and won't contain a itemid visible as parameter.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.