In Eclipse Ditto versions 3.0.0 to 3.9.6, the Things service fetches WoT (Web of Things) ThingModels over HTTP from URLs supplied by API users in the definition field of a Thing or Feature, without validating the target host, and follows HTTP redirects without re-validating the redirect target and without a hop limit. An authenticated user who is permitted to create a Thing, or who holds WRITE permission on an existing Thing, can thereby cause the Things service to issue arbitrary HTTP GET requests from inside the deployment's network — including to cloud instance-metadata endpoints and other internal services — and can use the differing error responses returned to the caller to enumerate internal services. Versions 2.4.0 to 2.5.x contain the same code, but are only affected where the operator explicitly enabled the WoT integration feature toggle, which is disabled by default in those versions.