Fortnightly Topic Challenge #11: Steganography

This is the eleventh installment of the Fortnightly Topic Challenge described here, with topics suggested and voted for here. This fortnight's topic is (suggested by Alconja), and will span from June 24th – July 8th. During this period, we will compile the list of questions featuring this topic and post it as an answer to this question.

In the meantime, please go propose and vote on future challenges!

Everyone have fun, and happy puzzling!!

• Here's the tag wiki for steganography: Hidden messages concealed in otherwise unsuspicious pictures, text, and/or audio. – haykam Jul 3 '16 at 2:36
• @Emrakul When exactly do we start new Fortnightly challenges? Is it time for the 12th by now? – BmyGuest Jul 13 '16 at 7:45
• @BmyGuest I'm not sure! There's no set time, I think. We've just been going with "whenever someone wants to start the top-voted challenge," to this point, I think. – user20 Jul 13 '16 at 7:46