Is it ensure, insure, or assure?
magic bullet mag·ic bullet (māj'ĭk)
A drug, therapy, or preventive therapy that cures or prevents a disease.
A miraculous remedy for some social, economic, etc, ill: We know no one chancellor has a magic bullet to turn the school system around
[1960s+; fr the name given in 1910 to salvarsan, formerly a trademark, discovered and proposed by the bacteriologist Paul Ehrlich as a cure for syphilis]