Noticed this too, could be from one of those EVAP/Fuel lines above it.Looks to me more like a leak coming down from something above the axle.
These have reusable seals on the diffs. I know it sounds crazy.Noticed this too, could be from one of those EVAP/Fuel lines above it.
Otherwise I also agree with others that it's most likely the diff cover seal. You'd be surprised how many people can't install those seals, or use gasket maker correctly.