I'm surprised no one has typed this yet, despite it being the Maquarie Dictionary word of the year.
By the way, it means a story that seems innocent at first, but escalates into something bad after further investigation. Take the coiner of the word's short story, for example:
The whole internet loves Milkshake Duck, a lovely duck that drinks milkshakes! *5 seconds later* We regret to inform you the duck is racist. See also Internet.