Bizarre electrical set-up for bathroom light fixture
This is a common hack for ungrounded outlets.  Sometimes you see just loose wires, sometimes like this someone will use a new cable.  The worse I've seen is someone stringing lamp cord around to use as an add on ground.  The lack of a junction box is another issue.

For safety this should be replaced by a professional.  A new grounded cable should be run from the main service panel and a GFCI protected outlet to replace the outlet on the light.  The cloth wiring does not get better with age.