After I saw your message, I went out to look at my abutilon.  The plant is deciduous and with the sudden change in the weather, I think this is just part of the normal cycle of the plant.  If your plant is in a pot, now would be a good time to determine where you want to place it for protection.  Mine is in the ground in a relatively protected spot so I intend to mulch it heavily like I did last year and it made it through the  winter nicely.  I won't do it until all the leaves have dropped which is the sign the plant has gone dormant.  the same would apply if you plan to store the plant in your garage or shed.