draw.io: Path traversal in ExportProxyServlet allows access to arbitrary backend endpoints

Summary

draw.io is a configurable diagramming and whiteboarding application. Prior to version 30.2.7, src/main/java/com/mxgraph/online/ExportProxyServlet.java uses request.getPathInfo() to build a proxyPath and appends it directly to EXPORT_URL without rejecting dot segments or confirming that the normalized destination remains under the configured export path. An unauthenticated request containing traversal segments can therefore address unintended routes on the internal export server, and the servlet forwards all request headers and the request body to that destination, allowing arbitrary header injection. Depending on the export service configuration, exploitation can expose administration, debugging, health, or configuration endpoints and can permit unintended internal actions. This issue is fixed in version 30.2.7.