Using ST-link for 1.8V target voltage
The ST-LINK/V2 has a dedicated pin TVCC (target VCC) to detect the voltage of the application board and to ensure that the right voltages are used.

Usually the detected voltage is reported by the utility used for programming and can be inspected before the programming is initiated.

So it should be safe to connect this pin and try to see if the target voltage is detected correctly.