Given a Cartesian fibration $p : \mathbf{E} \to \mathbf{B}$ over an $\infty$-topos the paper by Marc Hoyois mentioned in his answer to this question gives some sufficient conditions for $\mathbf{E}$ to be an $\infty$-topos. I'd like to know when the converse holds. That is, if we have a functor between toposes $p : \mathbf{E} \to \mathbf{B}$, when it is a Cartesian fibration? Since this question is probably too general, it may be assumed that $p$ is the direct image of a geometric morphism and even more that it is the global section functor $\mathrm{Hom}(1,-) : \mathbf{E} \to \mathrm{\infty Grpd}$.

More generally, if $\mathbf{C}$ is an arbitrary $\infty$-category with a terminal object, when the functor $\mathrm{Hom}(1,-) : \mathbf{C} \to \mathrm{\infty Grpd}$ is a Cartesian fibration? Since this question is also probably too general, it may be assumed, if it helps, that $\mathbf{C}$ is locally presentable and that $\mathrm{Hom}(1,-)$ has either left or right adjoint.