With the advent of the era of big data, processing massive amounts of data requires powerful computing servers, and outsourcing to the cloud has become the main way for customers to solve the shortage problem of computing power. However, due to the commercial nature of cloud service providers, it brings a certain threat to the security of outsourcing. How to implement secure iterative outsourcing computation to the cloud is a very challenge problem, although there are some algorithms for solving this problem, but we show in this paper some algorithms are not secure. By iterative using some strategy the adversary will finally compute all entries of some private matrix, which will be sufficient to break the IND-CPA security of secure outsourcing algorithms.