  We present an analysis of the intrinsic (unattenuated by the extragalactic
background light, EBL) power-law spectral indices of 128 extragalactic sources
detected up to z~2 with the Fermi-Large Area Telescope (LAT) at very high
energies (VHEs, E>50 GeV). The median of the intrinsic index distribution is
2.20 (versus 2.54 for the observed distribution). We also analyze the observed
spectral breaks (i.e., the difference between the VHE and high energy, HE, 100
MeV<E<300 GeV, spectral indices). The LAT has now provided a large sample of
sources detected both at VHE and HE with comparable exposure that allows us to
test models of extragalactic gamma-ray photon propagation. We find that our
data are compatible with simulations that include intrinsic blazar curvature
and EBL attenuation. There is also no evidence of evolution with redshift of
the physics that drives the photon emission in high-frequency synchrotron peak
(HSP) blazars. This makes HSP blazars excellent probes of the EBL.
