Actually most explosive devices used by terrorists nowdays are a bit more sophisicated than flash or pyrotechnic firework compositions
In Bali they used >1100 KG of KCLO3/AL/S in a van according to wikipedia.
The bomb
The Mitsubishi L300 van bomb was initially thought to have consisted of C4, a military grade plastic explosive which is difficult to obtain. However, investigators discovered the bomb was made from potassium chlorate, aluminum powder, and sulfur. For the Sari club bomb with the L300 van, the terrorists assembled 12 plastic filing cabinets filled with explosives. The cabinets, each containing a potassium chlorate, aluminum powder, sulfur mixture with a TNT booster, was connected by 150 meters of PETN-filled detonating cord. Ninety-four RDX electric detonators were fitted to the TNT. The total weight of the van bomb was 1.125 tons.[10] The large, high-temperature blast damage produced by this mixture was similar to a thermobaric explosive,[11] although the bombers may not have known this.[12]