CVE-2026-35485: text-generation-webui has a Path Traversal in load_grammar() — arbitrary file read without authentication

text-generation-webui is an open-source web interface for running Large Language Models. Prior to 4.3, an unauthenticated path traversal vulnerability in load_grammar() allows reading any file on the server filesystem with no extension restriction. Gradio does not server-side validate dropdown values, so an attacker can POST directory traversal payloads (e.g., ../../../etc/passwd) via the API and receive the full file contents in the response. This vulnerability is fixed in 4.3.