  Advanced Virgo end benches were a significant source of scattered light noise
during the third observing run that lasted from April 1 2019 until March 27
2020. We describe how that noise could be subtracted using auxiliary channels
during the online strain data reconstruction. We model in detail the scattered
light noise coupling and demonstrate that further noise subtraction can be
achieved. We also show that the fitted model parameters can be used to
optically characterized the interferometer and in particular provide a novel
way of establishing an absolute calibration of the detector strain data.
