Strange debuffs in the jungle

So one day, I was playing as Rek'Sai in the jungle. I got a with her and everything seemed normal. That was until I bought a Black cleaver, and I was getting some interesting debuffs. Whenever a neutral monster attacked me, I would receive my own black cleaver debuff, and having my armor reduced. It wasn't just on monsters that fought back, but even the Scuttle Crab was applying the debuff. I inspected it with a few more items, such as , and it too was applying the items debuff on me when I was attacking monsters. It also works with Red Buff, slowing my movement speed and adding a true damage DOT. I hope this isn't something Riot put in here secretly, and that it is actually a bug. Can I get some feedback whether this is a bug or not?