Police were called at 21:15hrs on Thursday, 26 February, to a report of shots fired through a window at a house in the Market Street area of East Ham, E6.
A woman aged in her 70s sustained injuries to her arm. She was taken to hospital by ambulance and has since been discharged.
Officers from Trident are investigating.
There has been no arrest at this early stage. Enquiries are ongoing.
Anyone who witnessed the incident or has information that may assist the inquiry should call police on 101 or, to remain anonymous, call Crimestoppers on 0800 555 111.