---
summary: format-parity numeric normalization rejects lossy digit-shift transforms while preserving locale support; fetchWithTimeout SSRF guard documented as best-effort with DNS-rebinding caveat
breaking: false
---

# 0.7.3 — 2026-04-24

Two small follow-ups to v0.7.0/v0.7.1 work. The format-parity numeric normalization landed in [#54](https://github.com/cyanheads/mcp-ts-core/pull/57) widened too far — it accepted lossy decimal-shift transforms because it stripped both `,` and `.` globally before the sentinel match. The SSRF helper docs claimed more than they deliver: there's a real DNS-rebinding / TOCTOU window between the helper's pre-validation lookup and `fetch`'s own resolution.

## Fixed

- **`format-parity` numeric normalization preserves decimal marks ([#58](https://github.com/cyanheads/mcp-ts-core/issues/58))** — replaces the global `,`/`.` strip with a context-aware `THOUSANDS_GROUP_PATTERN` (`\b\d{1,3}(?:[SEP]\d{3})+\b`) that only collapses separators flanked by the canonical digit-grouping shape. Lossy transforms (`value / 10` rendered as `90,000,000.1`, `value / 100` as `9000000.01`) now correctly fail parity instead of false-positive matching. Mainstream locales preserved: en-US, de-DE, fr-FR, tr-TR, pt-BR, nl-NL, sv-SE, es-ES, de-CH all still pass via `toLocaleString` / `Intl.NumberFormat`. Acknowledged tradeoff: Indian lakh/crore groupings (`hi-IN`'s `90,00,00,001` — groups of 2 after the initial 3) don't fit the `\d{3}` shape and now fail parity where they previously passed via the global strip; documented inline as an acceptable cost to reject digit-shift transforms.

## Documentation

- **`fetchWithTimeout` SSRF guard reframed as best-effort ([#60](https://github.com/cyanheads/mcp-ts-core/issues/60))** — adds explicit DNS-rebinding / TOCTOU caveat to `FetchWithTimeoutOptions.rejectPrivateIPs`, `assertNotPrivateUrl`, and `assertDnsNotPrivate` JSDoc. Node's pre-validation `dns.resolve4`/`resolve6` lookup is independent from the native `fetch` call's own resolution, so a malicious authoritative DNS server (or a low-TTL race) can return a public IP at validation and a private IP at fetch time. Workers path further restricted to literal-hostname/IP checks (no DNS API at the edge). Guidance updated to recommend network egress controls, a DNS-pinning fetch proxy, or a custom resolver that pins the validated address for strong SSRF isolation. `skills/api-utils/SKILL.md` row updated with matching language. No runtime behavior changes.
