Aggressive fermentation is pretty common and it can be pretty common place in carboys due to a less headspace between the wort and airlock. I'd recommend throwing a blow-off tube on that carboy immediately. If you're limited on home brew supplies you might be able to take a siphon tube from your racking cane and slipping it on your airlock and then dunking the other end into a large pot of sanitizer solution.
In regards to contamination you are definitely at risk of it happening, but since your fermentation has already started your yeast should help fight off any other bugs that get into the wort and the alcohol that has already been created might offer some protection.
15 Gallons of New England Hard Cider - Four yeasts: Ale yeast, two cider yeasts, and a champagne yeast.
Helliday Ale and Chocolate Nitro Stout