  The AMS experiment onboard the International Space Station has recently
provided cosmic ray electron and positron data with unprecedented precision in
the range from 0.5 to 350 GeV. The observed rise in the positron fraction at
energies above 10 GeV remains unexplained, with proposed solutions ranging from
local pulsars to TeV-scale dark matter. Here, we make use of this high quality
data to place stringent limits on dark matter with masses below ~300 GeV,
annihilating or decaying to leptonic final states, essentially independent of
the origin of this rise. We significantly improve on existing constraints, in
some cases by up to two orders of magnitude.
