Security vulnerability with MAX CPLD's !!

You have the Cyclone III LS family which is more targeted on security and protection against tempering and cloning.

But nothing is bullet proof. You can make it more difficult to reverse engineer a system, but to someone with unlimited resources anything is crackable. You just need to make it hard enough so that it isn't economically viable.

As for the Max V... I didn't find in the datasheet how the configuration is transferred from the internal flash to the SRAM registers during power up. If this transfer is done serially, then in theory it could be possible to get the configuration stream back by carefully monitoring the power supply. That said I rather think that it is a parallel interface, and in that case getting the stream back is near impossible in this way. The only way to get the configuration would then be to open the chip and do a more invasive attack, which would require extensive knowledge and equipment.