In 2005, Kellogg's decided to lower the salt levels in the Corn Flakes cereal, which potentially could have altered the taste of the cereal. Since that change in 2005, there is no evidence that the recipe has been changed.
The Kellogg website explains how the cereal was created. Since then, there was one change in 2005 after careful testing. There are health reasons as to why the recipe was altered, which encouraged the lower salt levels.
In the testing, most people actually preferred the Corn Flakes with less salt. Other than this instance, the recipe has remained mostly the same throughout the history of the company.