  The copper oxides present the highest superconducting temperature and
properties at odds with other compounds, suggestive of a fundamentally
different superconductivity. In particular, the Abrikosov vortices fail to
exhibit localized states expected and observed in all clean superconductors. We
have explored the possibility that the elusive vortex-core signatures are
actually present but weak. Combining local tunneling measurements with
large-scale theoretical modeling, we positively identify the vortex states in
YBa$_2$Cu$_3$O$_{7-\delta}$. We explain their spectrum and the observed
variations thereof from one vortex to the next by considering the effects of
nearby vortices and disorder in the vortex lattice. We argue that the
superconductivity of copper oxides is conventional, but the spectroscopic
signature does not look so because the superconducting carriers are a minority.
