Are you referring to what they describe as "ghosts" in the image description? > Another signature of Euclid special optics is the presence of a few, very faint

Are you referring to what they describe as "ghosts" in the image description? > Another signature of Euclid special optics is the presence of a few, very faint and small round regions of a fuzzy blue colour. These are normal artefacts of complex optical systems, so-called ‘optical ghost’; easily identifiable during data analysis, they do not cause any problem for the science goals.