DIAGNOSIS Yeah, this one's common. The spotlight is supposed to turn off automatically after a set time, but sometimes the "Auto" setting in the schedule gets overridden or glitches, leaving it manually set to "On."
FIX Open the Arlo app, tap on the camera's settings, then go to Device Utilities > Light Settings. Make sure the switch for the spotlight is set to Auto (not 'On' position). While you're there, tap 'Schedule' and verify it's set to activate only during your desired hours (like sunset to sunrise).
IF THAT DIDN'T WORK A buggy firmware can cause this. Check for updates in the app under Settings > My Devices > select your camera > Device Info > Firmware. If an update is available, install it with the camera on the charger. After updating, reboot the camera from the same settings menu.
HEADS UP If you have it set to 'Auto' but it's still stuck on, the ambient light sensor might be obstructed by a cobweb or dirt. Give the lens and the small sensor window next to it a quick wipe with a microfiber cloth.