Splices should be enclosed in approved boxes.
I really hope that skinny wire isn't carrying 120 volts....it looks almost thin enough to be telephone or door-bell wire....
Also, it seems to me that that black conductor is 300-ohm twin-lead wire used for TV and FM radio antennas. Please tell me that stuff is NOT connected to the Romex!!!
At least they used the proper tape for splices. Could have been worse -- either paper "masking" tape or duct tape.