1. A computer-readable storage medium encoded with computer-executable instructions that, when executed by one or more computers, cause the computers to: receive a plurality of templates comprising input data for an application; perform application tracing of the application as the application reads and processes the data contained in the plurality of templates to produce operation mapping data, wherein the operation mapping data is produced without requiring source code for the application, knowledge of a syntactical structure of the input data, or specially instrumented application modules; receive a target operation in the application; generate input data from the plurality of templates by fuzzing one or more data locations in the data contained in the plurality of templates based on the operation mapping data and the target operation; and cause the application to read and process the generated input data.