Are you talking about simply combining files? This is an old trick people have used for ages to get around file type limitations. Like members of 4chan would combine zip files with jpegs and upload them. All you had to do was open it with an zip program to access the files or change the extension from jpg to zip. I am pretty sure 4chan has blocked this and I imagine a lot of social media sites have too.
I remember hearing about someone combining a certain type of illegal photos to mp3s of popular songs and sharing them on p2p networks so thousands of others were hosting his illicit porn stash for him.