You've had a touch up at some point, they've removed the light fittings but left the bulbs dangling whereby they've gained a bit of overspray in the process.
Lazy paint job as they haven't masked the car up fully.
My car had it too, rear bumper plate replaced but bumper resprayed (it's got a bit of an eggshell texture where the under layer is slightly cracked).
every used car has been touched up either using a company like chips away or a spray shop given the location probably scratches have been painted over on the rear lights or more likely the rear quarter panel was repainted
Yeah, I'd say the lower bumper panel was removed and the upper part was given a squirt for sure, everyone scuffs a bumper at some point.