The security patch adds path normalization to the request handler callback within module.exports.listen. In vulnerable versions, this anonymous callback function (passed to http.createServer) processes raw pathname from the URL without normalization, allowing path traversal. While the function itself is anonymous, it is contained within and executed by the exported listen method. Runtime profiling would show execution flow through module.exports.listen when handling malicious requests, as this is the root function that configures the server and contains the vulnerable path handling logic.