The Chang model is the smallest model of ZF containing every countable set of ordinals. Forcing over a variant of the Chang model of determinacy, we obtain a model of ZFC satisfying the theory in which Jensen's square principle fails at $\omega_{3}$ and $\omega_{4}$. In this model, the Iterability Conjecture fails for the Mitchell-Schindler version of $\sf{K}^c$. This is joint work with Grigor Sargsyan.