Is overclocking only dangerous if you increase the voltage?

[KABAZZ_]

I was thinking of overclocking my gtx 950m through msi afterburner. Is there risk of my GPU overheating if I don't touch voltage controls?

 

[Gam3r01]

Any form of OCing is going to produce more heat, adding voltage simply increases it faster/allows for higher clock speeds.
I highly recommend against overclocking a mobile GPU, if the cooling system were capable of running those clocks at a reasonable rate, it would be clocked at that speed stock.