To keep delegates' brains busy during VB2015 even when there were no talks to attend, there was a puzzle to solve.
The puzzle was the second stage of a competition. The first stage of the competition consisted of finding a clever way to hide a URL inside the image shown below. This could be done by making small modifications to the colours of the image, by using obscure fields from the image specification, or by using other kinds of steganography — and of course you could use multiple stages to hide the URL.
The second stage of the competition, the puzzle-solving stage, then took take place during the conference. Competition entrants were given the images others had constructed and their task was to find the URLs hidden inside them.
The winner of the competition was hasherezade from Malwarebytes.