  The validity of the cosmic censorship conjecture for the Kerr-Sen black hole,
which is a solution to the low-energy effective field theory for
four-dimensional heterotic string theory, is investigated using charged
particle absorption. When the black hole absorbs the particle, the charge on it
changes owing to the conserved quantities of the particle. Changes in the black
hole are constrained to the equation for the motion of the particle and are
consistent with the laws of thermodynamics. Particle absorption increases the
mass of the Kerr-Sen black hole to more than that of the absorbed charges such
as angular momentum and electric charge; hence, the black hole cannot be
overcharged. In the near-extremal black hole, we observe a violation of the
cosmic censorship conjecture for the angular momentum in the first order of
expansion and the electric charge in the second order. However, considering an
adiabatic process carrying the conserved quantities as those of the black hole,
we prove the stability of the black hole horizon. Thus, we resolve the
violation. This is consistent with the third law of thermodynamics.
