  A wide-angle Cerenkov array TAIGA-HiSCORE (FOV $\sim$0.6 sr), was originally
created as a part of TAIGA installation for high-energy gamma-ray astronomy and
cosmic ray physics. Array now consist on nearly 100 optical stations on the
area of 1 km$^2$. Due to high accuracy and stability ($\sim$1 ns) of time
synchronization of the optical stations the accuracy of EAS arrival direction
reconstruction is reached 0.1$^\mathrm{o}$. It was proven that the array can
also be used to search for nanosecond events of the optical range. The report
discusses the method of searching for optical transients using the HiSCORE
array and demonstrates its performance on a real example of detecting signals
from an artificial Earth satellite. The search for this short flares in the
HiSCORE data of the winter season 2018--2019 is carried out. One candidate for
double repeater has been detected, but the estimated probability of random
simulation of such a transient by background EAS events is not less than 10%,
which does not allow us to say that the detected candidate corresponds to a
real astrophysical transient. An upper bound on the frequency of optical spikes
with flux density of more than $10^{-4} \mathrm{erg/s/cm}^2$ and a duration of
more than 5\,ns is established as $\sim 2 \times 10^{-3}$ events/sr/hour.
