The word oversight has two opposing meanings that can be confusing:

1. A mistake caused by not noticing something important. If you forget to add your name to the top of your homework, that's an oversight. When a baker leaves salt out of a recipe by accident, it's an oversight. This type of oversight happens when you're working quickly or your attention slips for a moment. The mistake isn't intentional: you simply overlooked something you should have caught.
2. Watchful supervision or management. When a school principal provides oversight of the cafeteria, she makes sure everything runs properly and safely. Congressional committees provide oversight of government agencies, checking that they follow the rules and spend money appropriately. This meaning is almost the opposite of the first: instead of missing something, you're carefully watching to make sure nothing gets missed.

The context usually makes clear which meaning applies. If someone says “due to an oversight,” they mean a mistake. If they say “under the oversight of,” they mean supervision. The two meanings actually connect: good oversight (supervision) helps prevent oversights (mistakes).