  Supermagnified stars are gravitationally lensed individual stars that are
located close to a caustic of a lensing galaxy cluster, and have their flux
magnified by a large enough factor (typically ~ 1000) to make them detectable
with present telescopes. The maximum magnification is limited by microlensing
caused by intracluster stars or other compact objects, which create a network
of corrugated critical lines with an angular width proportional to the surface
density of microlenses. We consider a set of 9 cases of supermagnified stars
reported in the literature, and derive an upper limit on the surface density of
compact objects, such as primordial black holes, that might be present as a
fraction of the dark matter in addition to known intracluster stars. Any such
additional compact objects would widen the corrugated critical line network and
therefore the width of the distribution of supermagnified stars around the
modeled critical lines of the lens. We find that any compact objects, including
primordial black holes, with masses above $\sim 10^{-6}\, M_{\odot}$ (for which
the microcaustics are smaller than the typical angular size of supermagnified
stars) cannot account for more than ~ 3% of the dark matter.
