This is the thirty-first installment of the Fortnightly Topic Challenge described here, with topics suggested and voted on here. This fortnight's topic is steganography (suggested by Mithrandir), and will span from the the 5th of June to the 18th of June. During this period, we will compile the list of questions with this tag and post it as an answer to this question.
In the meantime, please go and propose and vote on future challenges!
Everyone have fun, and happy puzzling!
Link to other Fortnightly Topic Challenges.