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CVE-2026-13447 – Authentication Bypass (JWT Forgery) – MStore API WordPress Plugin ≤ 4.20.0

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Summary

CVE-2026-13447 is a critical Improper Authentication (CWE-287) vulnerability in the MStore API – Create Native Android & iOS Apps On The Cloud WordPress plugin, affecting versions up to and including 4.20.0. The flaw allows unauthenticated attackers to forge Firebase Phone Auth JWTs and impersonate any phone number, gaining unauthorized access to existing WordPress accounts or creating new arbitrary accounts. It carries a CVSS v3.1 score of 9.8 (Critical).

Technical details

  • Root cause: the FirebasePhoneAuthHelper::verify_id_token() function decodes and checks Firebase ID token claims (alg, kid, aud, iss) but never validates the JWT’s cryptographic signature against Google’s public key certificates.
  • Trigger conditions: an attacker generates their own RSA key pair, signs a JWT with arbitrary phone-number claims, and submits it to the plugin’s Firebase phone-authentication REST endpoint.
  • Attack vector: network, no authentication or user interaction required (AV:N/AC:L/PR:N/UI:N).
  • Impact: full authentication bypass — account takeover of existing users or creation of arbitrary new WordPress accounts, with high impact to confidentiality, integrity, and availability.

Affected software

  • MStore API – Create Native Android & iOS Apps On The Cloud (WordPress plugin, by inspireui): versions up to and including 4.20.0

Severity

CVSS v3.1 Base Score: 9.8 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: upgrade the MStore API plugin to version 4.21.0 or later, which introduces Firebase JWT signature and audience validation.
  • If immediate patching is not possible: disable or restrict access to the Firebase phone-authentication REST endpoints, and monitor for unexpected new user account creation or logins tied to phone-based authentication.

References

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