Security vulnerability with MAX CPLD's !!

Sorry I didn't see that you were using a Max 3000A and not a Max V. In that case it makes things a lot harder, as the Max 3000 doesn't use a separate configuration memory but has EEPROM cells directly integrated in the LABs. In this case there is no way to access the configuration by probing the power supply or trying to trigger errors that way, as there in no configuration data loading. The only solution I see to get back the data in that case is either through a magical undocumented JTAG command (which I'm not aware of, and I don't think Altera would have done this) or by opening the chip and trying to make that bit change in some way. So this doesn't change what I said, while it isn't impossible it requires lots of knowledge and equipment, and probably isn't cheap.