Summary From v1.13.2 through v1.18.0, oasdiff did not enforce "--allow-external-refs=false" (library: "openapi3.Loader.IsExternalRefsAllowed = false") when loading a spec from a git revision (the "rev:path" form, e.g. "main:openapi.yaml"). External "$ref"s were resolved on that load path even when external refs were explicitly disabled, so the mitigation silently did not apply there. Impact A caller who set "--allow-external-refs=false" specifically to safely process untrusted specs remained exposed — on the git-revision load path only — to: - SSRF via "$ref: "http://<internal-host>/…"", and - Local file reads via "$ref: "/path"" or "file://". Affected callers: - CLI: "oasdiff diff main:openapi.yaml HEAD:openapi.yaml --allow-external-refs=false" (and "breaking" / "changelog" / "summary", and the "git-diff-driver") run over untrusted spec content. - Go library consumers of "github.com/oasdiff/oasdiff/load" that set "IsExternalRefsAllowed = false" and load from a git-revision source via "load.NewSpecInfo". The file and URL load paths correctly enforced the setting; only the git-revision path was affected. Callers that left external refs at the default ("true") are not in scope for this advisory. Patches v1.18.1 enforces the external-refs policy on the git-revision path (so "--allow-external-refs=false" now blocks external "$ref"s there) and returns a dedicated exit code ("123") when an external "$ref" is refused. Workarounds - Upgrade to v1.18.1, or - Avoid the git-revision input form when processing untrusted specs with external refs disabled. Notes - Introduced in v1.13.2 (#832, which added "$ref"-chain resolution on the git-revision path); fixed in v1.18.1 (#974, #975). - The permissive default ("allow-external-refs: true") and its zero-interaction exposure in CI via the GitHub Action is tracked separately in GHSA-fhj3-7267-7vv5 (oasdiff-action).