A computer-implemented method, computer program product, and computer processing system are provided for generating an adversarial input. The method includes reducing, by a Conditional Variational Encoder, a dimensionality of each of inputs to a target algorithm to obtain a set of latent variables. The method further includes separately training, by a processor, (i) a successful predictor with a first subset of the latent variables as a first input for which the target algorithm succeeds and (ii) an unsuccessful predictor with a second subset of the latent variables as a second input for which the target algorithm fails. Both the successful and the unsuccessful predictors predict outputs of the target algorithm. The method also includes sampling, by the processor, an input that is likely to make the target algorithm fail as the adversarial input by using a likelihood of the successful predictor and the unsuccessful predictor.