The Firewall as spelled out in the original paper is widely considered to be unlikely, not in the least because it violates the equivalence principle. There are

The Firewall as spelled out in the original paper is widely considered to be unlikely, not in the least because it violates the equivalence principle. There are weaker versions of the firewall based in M-Theory which exist because there is no singularity, and the event horizon is actually the surface of the fuzzball which takes its place, but that’s a different sack of weasels.