ISIS already admitted the crime even releases photos of the bomb used to bring downed the plane.
You mean this one?
https://twitter.com/RT_com/status/667003886062972929/photo/1?ref_src=twsrc%5EtfwAccording to FSB, the TNT equivalent of explosive device was ~1.5 kg. Relative efficience for the most of industrially produced plastic explosive composition is in range from 1.1 to 1.25, so the minimum requred amount of explosive would be ~1.2 kg. It's too much for 0.33l can.
So this photo is just a fake, even if we would forget about these ridiculous red/green LEDs.
Looks like IS mostly consists of incompetent attention whores, who have wasted too much time on movies.