Most home exterior doors have deadbolt locks. Occasionally these locks are not installed properly. An improperly installed deadbolt could make it easy to unlock the door without using a key.
To check your lock for proper installation, first, try to lock the door while it is in the closed position mark where the twist knob is pointing. Next, open the door and turn the twist knob again. If the twist knob is able to go further than the marking, then the deadbolt may be easily pushed back into the fully unlocked position.
To fix this issue first remove the strike plate. Then choose an appropriately sized drill bit and drill out some extra room in the doorframe. This will allow the deadbolt to fully activate, making your home more secure.