  We examine the recently-reported low-energy electron recoil spectrum observed
at the XENON1T underground dark matter direct detection experiment, in the
context of new interactions with solar neutrinos. In particular we show that
scalar and vector mediators with masses $\lesssim 50$ keV coupled to leptons
could already leave a visible signature in the XENON1T experiment, similar to
the observed peak below 7 keV. This signals that dark matter detectors are
already competing with neutrino scattering experiments such as GEMMA, CHARM-II
and Borexino. If these results from XENON1T are interpreted as a new signal of
such physics, the parameters which fit the excess face challenges from
astrophysics which seem very difficult to overcome. If they are rather viewed
as a constraint on new couplings, they herald the start of an era of novel
precise probes of physics beyond the standard model with dark matter detectors.
