Szymon Sidor , A computer scientist and a blogger discovered a loop hole in android which makes the hackers able to take pics from the android camera and upload them to a private server without the user(victim) noticing anything.
There are a lots of Camera related apps and apps that have the permission to use camera are available on Google Play Store. Every such app needs visible application activity, that is the screen must be turned on when they work. To take a picture or to record a video the application needs to display a preview on the screen.
Sidor himself made a camera app for the Nexus 5 which displays a preview of 1 by 1 pixel. The application can use the Rear camera as well as the Front camera. With such a very very low resolution display the application can now take the pictures and can record a video as it is displaying the preview, as the user can’t notice it because there are around 445 pixels per inch on a nexus 5 device.
Thankfully Sidor made a video as a proof, which lets us know even more disturbing things such as the photos can be of high quality and then can even embed GPS data in them.