The key evidence comes from the commit diff showing the vulnerability was fixed by adding a path validation check in serveRequest. The added code explicitly checks if request.fullPath starts with the configured directory (self.dir), which was missing in vulnerable versions. This function handles core request processing and path resolution, making it the logical point where path traversal would occur when unvalidated. The direct correlation between the vulnerability description (lack of path validation) and the patched code confirms this as the vulnerable function.