The same thing happened to me last night.
I got a snapchat from "Me" so I was extremely confused, I opened snapchat and it asked me to sign in, I don't use snapchat much so I didn't think anything of it at the time, and I don't see anything so figured it was an error. Couple minutes later a bunch of my friends are replying with "wtf", and in my feed it said I messaged every single person in my contacts with some snapfroot ice cream ad.