This isn't the first time a Vita port has cropped up; as PlayStation LifeStyle reports, Amazon France listed a Game of the Year edition in the summer for PS3, Xbox 360, and the Vita. When approached about the USK rating, a Warner Bros representative told us, "We have no comment."
Injustice, developed by Mortal Kombat studio NetherRealm, landed on Xbox 360, PS3, and Wii U back in April. It notched four and a half stars in our review, Jordan saying "its dark thematic overtones and mature ideas explore the psychological dangers of power, the temptations of absolute authority and the effects of grief on the psyche of metahumans, all while delivering a polished, thrilling fighting game experience."
Update: Brazil's rating board (via @lifelower) lists Injustice GOTY for Xbox One, PS4, and PC as well as Vita and the three original platforms of PS3, Xbox 360, and Wii U. Eyebrow raised, Injustice, eyebrow raised.