DO NOT install the Prolific USB-to-serial driver; it will brick your computer.

I'm doing some peripheral development and need to use a USB-to-serial cable with a chipset made by Prolific. Apple's built-in driver does not make this device visible to applications, so I downloaded and installed one from Prolific.

It is profoundly defective and will prevent your computer from starting, even in Safe Mode. Fortunately I was able to boot in Recovery Mode, and once I realized I wasn't looking at the main drive's filesystem, I was able to use Terminal to find and remove the offending kext from /Library/Extensions.

It's called ProlificUSB something something, easily recognized. Should you be afflicted by it, boot into Recovery Mode (power up with Command-R held), go to Utilities / Terminal. and enter the following.

cd /volumes/boot/Library/Extensions

ls

Now look through the list and find the file with "prolific" in it. Then

rm -r [the name of the Prolific file]

Then restart.