The downgrade approach is the paintings of developer tihmstar, with further credit score going to winocm (kloader), pod2g (odysseus), and iH8sn0w (consulting) amongst others.
Obviously this downgrade means may have extraordinarily restricted use-case situations, as it's strictly restricted to the aforementioned firmware/hardware combinations. Nonetheless, it's an outstanding (no SHSH blobs wanted!) feat, while you believe how tricky Apple makes it to downgrade firmware at the present time.
What do you assume ?