  The discovery of a terrestrial-mass free-floating planet candidate in the
light curve of the star TIC 107150013 observed by the Transiting Exoplanet
Survey Satellite (TESS) has recently been announced. A short-duration (~0.5
day), low-amplitude (~0.06 mag) brightening in the TESS light curve was
interpreted as a short-timescale gravitational microlensing event. However, the
purported event occurred far from the Galactic center and the Galactic plane
(l~ 239 deg, b ~ -5 deg), on a relatively nearby (~3.2 kpc) star, making the
microlensing interpretation unlikely. Here, we report the archival photometric
observations of TIC 107150013 collected by the Optical Gravitational Lensing
Experiment (OGLE) from 2018 through 2020. The archival OGLE light curve reveals
periodic variability indicative of starspots on the surface of the star. The
presence of starspots indicates magnetic activity of the star, which may also
manifest as stellar flares. We interpret the brightening of TIC 107150013 seen
in the TESS data as the stellar flare. We present similar flaring stars
detected in the archival OGLE data, mimicking short-timescale, low-amplitude
microlensing events. Such stars may be a source of non-negligible false
positive detections in the planned space-based microlensing surveys.
