  In this work we investigate validity of the weak form of the cosmic
censorship conjecture in the interaction of Kerr-Sen black holes with neutral
test fields. Previous studies of the Klein-Gordon equation on Kerr-Sen
background imply that superradiance occurs for scalar fields. We show that
scalar fields can overspin a nearly extremal black hole into a naked
singularity, but the modes that could overspin an extremal black hole are not
absorbed due to superradiance. From Kerr analogy one can naively expect
superradiance to be absent for fermionic fields. In such a case overspinning
becomes generic and also applies to extremal Kerr-Sen black holes. This robust
violation of cosmic censorship cannot be fixed by backreaction effects which
are ignored in this work. These results are analogous to the Kerr case.
