  Unraveling the nature of dark matter (DM) stands as a primary objective in
modern physics. Here we present evidence suggesting deviations from the
collisionless Cold DM (CDM) paradigm. It arises from the radial distribution of
stars in six Ultra Faint Dwarf (UFD) galaxies measured with the Hubble Space
Telescope (HST). After a trivial renormalization in size and central density,
the six UFDs show the same stellar distribution, which happens to have a
central plateau or core. Assuming spherical symmetry and isotropic velocities,
the Eddington inversion method proves the observed distribution to be
inconsistent with potentials characteristic of CDM particles. Under such
assumptions, the observed innermost slope of the stellar profile discards the
UFDs to reside in a CDM potential at a > 97% confidence level. The extremely
low stellar mass of these galaxies, 10**3-10**4 Msun , prevents stellar
feedback from modifying the shape of a CDM potential. Other conceivable
explanations for the observed cores, like deviations from spherical symmetry
and isotropy, tidal forces, and the exact form of the used CDM potential, are
disfavored by simulations and/or observations. Thus, the evidence suggests that
collisions among DM particles or other alternatives to CDM are likely shaping
these galaxies. Many of these alternatives produce cored gravitational
potentials, shown here to be consistent with the observed stellar distribution.
