Challenge: Online Steganography is helping Santa to get his work done!

A PNG image of santa is attached.

This is a typical challenge. Just find the right tool/encoding schema by googling “Online Steganography”.

I had a positive hit on the second try, here is the link: https://stylesuxx.github.io/steganography/

I wanted to at least understand the method used here, so dived into the source. The code converts the PNG into a stream for RGBA bytes (4 for each pixel), then takes the lowest bit form R, G and B and builds a bit stream, 3 bits per pixel. Then just convert it into a byte stream, grouping each 8 bits into a byte.

Flag: xmas{SantaIsWaiwingAtYou}

What did I learn: Online tools! And a bit about steganography.