That could be dangerous. If the pin is in OUTPUT mode and in the LOW state and you have 5 V connected to it, that's a short. That will cause the current on the pin to exceed its maximum rating, which could cause permanent damage.
That could be dangerous. If the pin is in OUTPUT mode and in the LOW state and you have 5 V connected to it, that's a short. That will cause the current on the pin to exceed its maximum rating, which could cause permanent damage.