If they got it through stego They most likely would not have posted corrupted versions of the flag seeing it is a pain in the ass to find the thing in an image let alone extract the flag from the email attachment.
Originated apparently from a manga anime
https://www.pixiv.net/member_illust.php?mode=manga&illust_id=34155255
I however completely see it as even more legitimate somehow after finding minerva symbology so high up in the elite.