Aliens (or atleast we presume it's aliens) have radio broadcasted from a distant part of the universe. They have provided a method to create a nuclear weapon powerful enough to blow up the entire solar system (maybe even more than that).
Now any lab in the world that has access to even a tiny bit of nuclear fuel can build such a weapon in a matter of days.
There appears to be no simple way to control the release of energy of the weapon (though it may be possible after a great deal of research). This weapon could be used by anyone to blackmail the world, but only if they are able to convince everyone that they can sacrifice their (and everyone else's) lives to the cause.
Is it more likely that the governments of the world will be successful in forging an agreement to not use such a weapon, or is it likely that there will be major political instability globally and possible formation of a new world order (or even the end of the world)?
P.S. There is no further contact with the anonymous beings who have leaked this method, or any explanation given as to why.