Selenology Today – 2015 (pdf) and Lunar Networks blog report on a flash seen on the Moon by three members – Marco Iten, Raffaello Lena, Stefano Sposetti – of the Geological Lunar Research Group, an Italian group of advanced amateur observers. The flash was apparently produced by a meteoroid impact: Mare Nubium impact with plume captured and analyzed – Lunar Networks –
Under the assumption of a meteoroidal impact we argue that this post luminous event and its ever growing dimensions was likely caused by the sunlight reflection on ejected materials released by the impact. Thus, future high resolution orbital data, e.g., from LRO spacecraft (NAC images) could allow the detection of this crater. Because this event was captured only by one observer, we checked for satellite glints and evaluated the likelihood of a meteor hitting head on our atmosphere.
This map shows the location of the flash at Mare Nubium: