Firefox 23 does not have TLS v1.2, but Nightly will very soon. During March there have been very active development in NSS for TLS v1.2 and they are AFAIK check

Firefox 23 does not have TLS v1.2, but Nightly will very soon. During March there have been very active development in NSS for TLS v1.2 and they are AFAIK checking in bit by bit now.