Stirling-PDF: Internal Service Account API Key Disclosure via Pipeline Endpoint

Stirling-PDF is a locally hosted web application that facilitates various operations on PDF files. Prior to 2.9.0, the /api/v1/pipeline/handleData endpoint in app/core/src/main/java/stirling/software/SPDF/controller/api/pipeline/PipelineProcessor.java injects the STIRLING-PDF-BACKEND-API-USER API key into pipeline subrequests, allowing an authenticated ROLE_USER to retrieve the key through /api/v1/user/get-api-key, impersonate the internal service account, bypass normal rate limits, and access internal endpoints including /api/v1/info/requests/all and /api/v1/info/load/all. This issue is fixed in version 2.9.0.