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NoorQureshiNoorQureshi/ronin/skills/api/api-versioning/SKILL.md

api-versioning

Skill26 starsChanged 31 days agoMITView on GitHub

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.

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SKILL.md

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

  1. 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 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.

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