What are the implications of the “Three Attacks on Proof-of-Stake Ethereum” paper?

Recently there was a scientific paper published called "Three Attacks on Proof-of-Stake Ethereum" which got some media attention:

https://arxiv.org/abs/2110.10086

I'm wondering what the implications are of this paper. Are these attacks already fixed in the spec or do they even need to be fixed? Will this delay the merge?