By default, WhatsApp saves the photos and videos you receive to your camera's film. If you do not change this option, you may end up with items that you may not want mixed in with your personal photos. Fortunately, it is possible to change this setting.

On iOS, open Settings and go to the Discussions menu. You will then just need to disable the Save to Film option.

On Android, go to Settings and enter the Discussions menu. Turn off Media Visibility to stop showing recently uploaded media in your phone's gallery.