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CVE-2026-16257 – Unauthenticated Arbitrary Post Creation via Authentication Bypass – Arvow AI SEO Wr

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Summary

CVE-2026-16257 is an authentication bypass vulnerability (CWE-287) in the Arvow AI SEO Writer WordPress plugin (all versions prior to 1.5.4). The flaw allows unauthenticated attackers to exploit a type-juggling weakness in an improperly restricted REST endpoint when the plugin has not been configured with a webhook secret, enabling the creation of arbitrary posts and pages and disclosure of author account and taxonomy information. The vulnerability carries a CVSS v3.1 base score of 8.2 (High).

Technical details

  • Root cause: The plugin exposes a REST API endpoint intended to be secured by a webhook secret comparison. When the plugin has not been configured (i.e., no webhook secret has been set), the comparison logic is subject to PHP-style type juggling, allowing the access control check to be bypassed.
  • Trigger conditions: The plugin must be installed and left in an unconfigured state (no webhook secret set) — a common scenario for freshly installed or never-fully-set-up instances.
  • Attack vector: Network-based (AV:N); no authentication (PR:N) or user interaction (UI:N) is required to exploit the flaw.
  • Impact: Attackers can create arbitrary posts and pages on the affected WordPress site, and can disclose author account information and taxonomy data. This impacts content integrity (Integrity: High) and can expose limited confidential information (Confidentiality: Low); there is no direct impact on availability.

Affected software

  • Arvow AI SEO Writer WordPress plugin (also distributed as "journalist-ai") — all versions prior to 1.5.4

Severity

  • CVSS v3.1 Base Score: 8.2 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Mitigation and recommended actions

  • Immediate: Update the Arvow AI SEO Writer plugin to version 1.5.4 or later, which resolves the authentication bypass by properly securing the REST endpoint and its webhook secret validation logic.
  • If immediate patching is not possible:
    • Ensure the plugin’s webhook secret is explicitly configured (do not leave it unset), as the vulnerability is specifically exploitable when the plugin remains unconfigured.
    • Consider temporarily deactivating the plugin until it can be patched.
    • Monitor for unexpected post/page creation activity and review WordPress author/taxonomy data for signs of unauthorized access.
    • Restrict or monitor access to plugin-related REST API routes via a web application firewall where feasible.

References

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