It's basically saltwater with flavoring, which in this case must come from ribs (probably boiled) no doubt made into some kind of bouillon. However, it's really just to make the chicken breast more moist. Anyone can do that themselves with an injector and that way control the amount of salt. I've used salt free chicken broth combined with seasonings and melted butter to increase the moisture content in chicken breasts. I'd never buy them injected - it just increases the weight and the salt content is much too high.
What Are They Injecting Into Your Chicken? | Clean & Lean Revolution (cleanandleanrevolution.com)