In Eclipse Ditto versions 3.6.0 to 3.8.13 and 3.9.0 to 3.9.7, the Ditto Explorer UI loads its complete environment configuration, including the Ditto API URI and the OpenID Connect (OIDC) provider settings, from an arbitrary cross-origin URL supplied in the environmentsURL query parameter. It adopts this configuration without user confirmation and persists it in the browser's localStorage. A crafted link can therefore set an attacker-controlled OIDC authority with autoSso enabled. The UI then automatically starts a login at the genuine identity provider but exchanges the returned authorization code together with its PKCE code_verifier at an attacker-controlled token endpoint. This lets the attacker redeem the code for the victim's access and refresh tokens. Alternatively, an attacker-controlled api_uri causes the UI to send the victim's bearer token or Basic credentials to the attacker. Because the configuration is persisted, later visits to the UI without the crafted link repeat the token theft. In versions 3.9.0 to 3.9.7, the Swagger UI OIDC integration of the Helm chart and the Docker Compose deployment is affected in the same way, but requires the user to start the login. The issue is fixed in 3.8.14 and 3.9.8.