How do I install the API Versioning skill?

Run npx skillmds@latest add noorqureshi/api-versioning in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is API Versioning free to use?

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Who published API Versioning?

NoorQureshi (@noorqureshi) published this skill. Their other Agent Skills are listed on their SkillMD profile.

API Versioning by noorqureshi — Agent Skill

Name: API Versioning
Author: NoorQureshi

API Versioning

Find and attack old/shadow API versions that missed a fix — improper inventory management. Load when the API is versioned (/v1, /v2, /api/2021-01), on "old API", or after mapping the surface. Signals: version in path/header/subdomain, deprecated docs, mobile app using an older version.

NoorQureshi f40cda0 2.0 KB Updated Sep 17, 2026

File contents

API versioning attacks

When it applies

The API exposes multiple versions and a vulnerability fixed in the current version still lives in an older or undocumented one. Old versions rarely get the same auth, validation, or rate-limit hardening.

Why it works

Teams patch the latest version and leave /v1 (and /beta, /internal, dated versions) running for backward compatibility. Those endpoints often skip a fix, lack a new authz check, or expose fields later removed — same data, weaker guard.

Method

Enumerate versions: swap the version in path (/v1↔/v2↔/v3), header (Accept: application/vnd.api+json;version=1, X-API-Version), or subdomain (api-v1., legacy.). Fuzz with ffuf.
Diff behaviour: take a request that's now blocked/fixed on the current version and replay it against older ones — missing auth, mass assignment (→ api-mass-assignment), BOLA (→ api-bola), verbose fields, or no rate limit.
Mine sources for old versions: mobile apps, JS bundles, wayback, and public API docs often reference deprecated versions still live.
Re-test every known bug per version — a fix in v2 is often absent in v1.

Gotchas

A 404 on /v1 root doesn't mean v1 is gone — test specific known endpoints under it.
Header/media-type versioning is easy to miss vs path versioning — enumerate all three.
Old versions may lack rate limits, enabling brute force the new one blocks.

Verify success

A vulnerability reproducible on an older/undocumented API version that is patched or better-guarded on the current one.

References

OWASP API Security Top 10 (2023) API9; API inventory/versioning guidance.

---name: api-versioningdescription: Find and attack old/shadow API versions that missed a fix — improper inventory management. Load when the API is versioned (/v1, /v2, /api/2021-01), on "old API", or after mapping the surface. Signals: version in path/header/subdomain, deprecated docs, mobile app using an older version.---# API versioning attacks## When it appliesThe API exposes multiple versions and a vulnerability fixed in the current version still lives inan older or undocumented one. Old versions rarely get the same auth, validation, or rate-limit hardening.## Why it worksTeams patch the latest version and leave `/v1` (and `/beta`, `/internal`, dated versions) runningfor backward compatibility. Those endpoints often skip a fix, lack a new authz check, or exposefields later removed — same data, weaker guard.## Method1. **Enumerate versions**: swap the version in path (`/v1`↔`/v2`↔`/v3`), header (`Accept: application/vnd.api+json;version=1`, `X-API-Version`), or subdomain (`api-v1.`, `legacy.`). Fuzz with `ffuf`.2. **Diff behaviour**: take a request that's now blocked/fixed on the current version and replay it against older ones — missing auth, mass assignment (→ `api-mass-assignment`), BOLA (→ `api-bola`), verbose fields, or no rate limit.3. **Mine sources for old versions**: mobile apps, JS bundles, wayback, and public API docs often reference deprecated versions still live.4. **Re-test every known bug per version** — a fix in v2 is often absent in v1.## Gotchas- A 404 on `/v1` root doesn't mean v1 is gone — test specific known endpoints under it.- Header/media-type versioning is easy to miss vs path versioning — enumerate all three.- Old versions may lack rate limits, enabling brute force the new one blocks.## Verify successA vulnerability reproducible on an older/undocumented API version that is patched or better-guardedon the current one.## ReferencesOWASP API Security Top 10 (2023) API9; API inventory/versioning guidance.

Frequently asked questions