Apparently in some deranged groups, UwU means "rape me" or something of the like. The similar term OwO is also usually used by furries to say the user is noticing a male's genitals. Both may open up certain cans of worms, so don't use freely.
Of note, the words did have a tamer and safer origin. But you know, the Internet.
Blame youtube meme videos for my not proud knowledge of this...
Tell me more about furry culture, I am interested to hear your thesis.