After reading a few posts last night, I decided I would clean all the grounds. I stumbled apon the negative ground to the battery was so dry and cracked that when I was handling it, most of the rubber fell off. Now I have a cable that is more exposed than covered...

does this pose a serious risk?

What could happen if not fixed right away?

Could it be a temporary fix to wrap with electrical tape?

I tried to include a picture but I'm doing this from my phone and it was taking too long.

 

There's no serious risk with this. This doesn't require you to run out and get a new cable yesterday, but it needs addressing. The cause is most often corrosion and age. You can insulate the cable temporarily. It does need replacing before you lose the ground entirely. Obviously, by reading the previous threads, you see the need for having good grounds.