CVE-2026-78675: GitPython: Arbitrary local file content disclosure via [include] directive in untrusted .gitmodules (SubmoduleConfigParser never disables merge_includes)

Non-blind local file content disclosure (first line) of any file readable by the victim process, triggered purely by attacker-controlled repository content and one routine, read-only GitPython call. Bounded to one line per triggering file (parsing aborts at the first MissingSectionHeaderError), but that line very often is the secret — .env files (DATABASE_URL=..., API_KEY=...), single-line credential/token files, /etc/passwd’s root entry for host fingerprinting. The primitive additionally serves as a generic error-based file-existence oracle for arbitrary host paths. This is materially stronger than the already-fixed, explicitly blind GHSA-cwvm-v4w8-q58c (“Blind local file inclusion”, CVSS 4.0, git/refs/symbolic.py ref-name resolution) — that advisory’s own writeup states it cannot disclose content; this one does, verbatim, via a different module (git/config.py’s include resolution).