A method includes performing taint analysis of a computer program and determining an original set of paths from sources to sinks. Each path corresponds to a vulnerability. The method includes determining for each variable whose type is a collection and is accessed in one of the paths in the original set of paths whether the variable points to a concrete value whose internal state is not tainted according to the taint analysis. The method further includes, for each of the variables whose type is a collection found not to be tainted according to the taint analysis, determining all points in the computer program where a membership check against the collection is performed. The method also includes, for each of the points, determining corresponding paths and removing those paths from the original set of paths to create a reduced set of paths. Apparatus and computer readable program products are also disclosed.