Mechanisms for evaluating downgrader code in application code with regard to a target deployment environment. Downgrader code in the application code is identified. Based on an input string, an output string that the downgrader code outputs in response to receiving the input string is identified. One or more sets of illegal string patterns are retrieved. Each of the one or more sets of illegal string patterns is associated with a corresponding deployment environment. The illegal string patterns are string patterns that a downgrader identifies in the information flow for security purposes. A determination is made as to whether the downgrader code is compatible with the target deployment environment based on the one or more sets of illegal string patterns and the output string. An output indicative of the results of the determining is generated.