Bikes were reported to leak oil on the rear left side. For most bikes this is not a leak: this is chain lube. It collects in the pinion cover and runs down the engine. The chain out of the factory is coated with a very fine oil that is very liquid when warming up. As long as you don’t see the oil level decrease in the engine just forget about it and ride.
But is seems that a small number of bikes may be affected by a leak from the oil sump gasket.