Macchanger just temporarily changes your MAC address, hiding your PC’s true MAC address. The MAC is a unique identifier built into the hardware, that can uniquely identify your device.
So for example - if you’re conducting a covert pen-test (with permission) on a corporate network, you would use macchanger to hide your true MAC address. And rather than using a random MAC, which might alert the sys-admins that you’re there, because a new unknown device has connected. And if you use anything too obviously fake, it will look even more suspicious. So you might set macchanger to use the MAC of another device on the network.
So all macchanger does is spoof your MAC address. It has nothing to do with exploiting vulnerabilities. And it doesn’t expose you to any vulnerabilities either!