Is it safe to drive the pins of this AVR chip while it's unpowered?

For example, if I were to share a motor driver such that it can be driven by two microcontrollers, would either microcontroller be damaged while the other is unpowered, but is seeing the signal voltages on its pins from the other microcontroller?

EDIT: Because this was marked as a duplicate, here is some clarification. The MCU specified here is different from a different manufacturer. Though I'm not sure, their operation and limits would most certainly differ. This question was not about wether it'll 'weaken' the MCU but about if its safe to do so in the first place. IMO weaken would mean that it is possible but over time it'll degrade the performance of the MCU.