  Employing the Einstein-scalar field system, we demonstrate an approach for
proving high co-dimensional nonlinear instability of naked-singularity
solutions as constructed by Christodoulou in [18]. We further investigate the
censorship of Christodoulou's naked singularity and show that a tiny
anisotropic perturbation arising from the outgoing characteristic initial data
would lead to the emergence of an anisotropic apparent horizon, which covers
and censors the naked singularity. Our approach advances the hyperbolic
short-pulse method by not requiring the aid of additional large parameters, by
permitting the use of initial perturbations for the shear tensor and the
derivative of scalar field to be with finite $BV$ and $C^0$ norms, and by
allowing the initial perturbation to be arbitrarily small in scale-critical
norms. New elliptic arguments based on non-perturbative methods are also
developed.
