Sorry for asking what appears to be general knowledge, but what exactly is the claim? That he peeked during the solve? Performed moves during memorization? Had outside help to remind him of the memo or algs? And what are the times in question, since I presume they’re not currently on the WCA site?
3BLD: 26.19+2 at Mineirim Open Spring 2018
I don't remember the exact times for 4BLD and 5BLD, they were around 6 minutes for 4BLD and 9 minutes for 5BLD, both done at Campeonato Brasileiro 2018. The 5BLD solve would have been SAR.
There is no official claim on how exactly he cheated, although the WDC is convinced that he couldn't get those times legitimately. (Keep in mind that this is under re-evaluation). Quoting from Lorenzo's Facebook post:
"I’m going to end this post by saying that I also have a couple of ideas on how he cheated, but I have no proof. Hence, the one year ban. If I could prove what I think happened, Fabio would have been banned for at least three years. Since this is all speculation, I won’t disclose any of my opinions on the matter."