ITunes (The Zygon Isolation)

An application was installed on Petronella Osgood's computer by 10 May 2020. Its logo was a white circle with a multi-coloured outline and a multi-coloured musical note in its centre. (WC: The Zygon Isolation)

Behind the scenes
While the application was not named in WC: The Zygon Isolation, the application was named "iTunes" in the real world, where it also has significance to the Doctor Who universe.