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CVE-2026-16603 – Unauthenticated Sensitive Information Disclosure – Passster (Content Protector) Wor

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Summary

CVE-2026-16603 is an unauthenticated sensitive information disclosure vulnerability in the Passster (Content Protector) WordPress plugin. Versions before 4.3.6 fail to enforce category-based content protection on the WordPress core REST API, allowing unauthenticated attackers to read protected post content. The issue is rated High severity (CVSS 7.5).

Technical details

  • Root cause: The plugin does not enforce its category-based content protection at the WordPress core REST API layer, so access controls that apply to normal page rendering are not applied to REST API responses.
  • Trigger conditions: An attacker queries the core REST API endpoints for posts that belong to a protected category; no authentication or user interaction is required.
  • Attack vector: Network — remotely exploitable over HTTP against the site’s REST API.
  • Impact: Unauthenticated disclosure of the full content, title, and excerpt of category-locked posts, breaking the intended content restriction.

Affected software

  • Passster (Content Protector) WordPress plugin — all versions before 4.3.6.

Severity

  • CVSS v3.1 base score: 7.5 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: Update the Passster (Content Protector) plugin to version 4.3.6 or later.
  • If no patch can be applied: Restrict or disable unauthenticated access to the WordPress REST API (for example, limit REST access to authenticated users), and place category-locked content behind additional access controls until the plugin is updated.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw response body: /wp-content/plugins/content-protector/

References

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Map your entire attack surface (continously)

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Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

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IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

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By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

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Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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