Oil leak?
That is your spare tire well, open the trunk/hatch and empty the contents of your rear trunk space into a large bowl, combine ingredients, and using a whisk, stir vigorously until creamy texture is achieved...
???
...sorry, woke up to this post, was still thinking about last night's dinner...
Those are "knockout" plugs - they help you drain out whatever got in the trunk - spilled milk, small gas can leak - small children that climbed into the back never to be found again during the last hide and seek game they played...
If you recently bought this used, you might want to reconsider the purchase...
The "fuel tank" is ahead of that wheel well - so if it's leaking - then the source of the leak is not from the spare tire section - it's further ahead before that rear crossmember.
The leak you're showing in the photo - if from the knockouts used in the spare tire well, is supposed to be from a DRY spare tire wheel well - whatever got in there to leave an oily residue - *ahemn*
You're just going to have to open it to find and remove the source of that leak...