Good catch, I don't know anything about what they are doing with that.
You may well be right about this.  It will depend on the facts.
If Poloniex is putting together these baskets, or has an interest in them, or is involved in some way other than merely posting bid and ask prices, they could have problems.
If these are just items that someone else, jl777 maybe, is putting up for sale, and poloniex is merely acting as the electronic communication network, they could very well be in the clear on this too.

If I were their legal adviser I might suggest that they seek out a No-Action letter from the SEC and clearly define their involvement with the questionable issues.