  A search for the exotic decay of the Higgs boson to a pair of light
pseudoscalars, each of which subsequently decays into a pair of photons, is
presented. The search uses data from proton-proton collisions at $\sqrt{s}$ =
13 TeV recorded with the CMS detector at the LHC that corresponds to an
integrated luminosity of 132 fb$^{-1}$. The analysis probes pseudoscalar bosons
with masses in the range 15-62 GeV, coming from the Higgs boson decay, which
leads to four well-isolated photons in the final state. No significant
deviation from the background-only hypothesis is observed. Upper limits are set
on the product of the Higgs boson production cross section and branching
fraction into four photons. The observed (expected) limits range from 0.80
(1.00) fb for a pseudoscalar boson mass of 15 GeV to 0.26 (0.24) fb for a mass
of 62 GeV at 95% confidence level.
