Security researcher has discovered a novel steganography technique for hiding data inside a Portable Network Graphics (.PNG) image file posted on Twitter. David Buchanan demonstrated how he could hide both MP3 audio files and ZIP archives within the PNG images hosted on the social-media platform. Twitter strips unnecessary data from PNG uploads, but they don t remove trailing data from the IDAT stream inside the DEFLATE chunk if the overall image file meets the requirements to avoid being re-encoded.
Source: https://threatpost.com/researcher-hides-files-in-png-twitter/164881/