Apparently, an years ago, there was reentrancy exploit on uniswap that was caused by ERC777 functionality: "Technically, the main logic behind these two incidents is the incompatibility between ERC777 and those DeFi smart contracts, which might be misused by the attacker to utterly hijack a normal transaction and perform additional illicit operations."
There are some other records of ERC777 causing major exploits in Uniswap, I wasn't able to confirm if it was the same case like this, and if it was legit in general, here is the little review from openzeppelin forum: https://blog.openzeppelin.com/exploiting-uniswap-from-reentrancy-to-actual-profit/ that might be the most trusted source so far.
The question is since V3 contracts came out, was this fixed? Did they make ERC777 compatible with new contracts?
P.S I will ask around with Uniswap support too and will post an answer if I get one, I'm sure this is a very sensitive subject and must be answered ASAP