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CVE-2026-66672 – Unauthenticated PHP Object Injection – Flatastic WordPress Theme ≤ 2.0

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Summary

CVE-2026-66672 is an unauthenticated PHP Object Injection vulnerability (CWE-502, Deserialization of Untrusted Data) affecting the Flatastic WordPress theme, versions 2.0 and earlier. The flaw allows a remote, unauthenticated attacker to trigger deserialization of untrusted data supplied to the theme, which can lead to object injection and, depending on other code ("gadget chains") present on the site, further compromise. The issue is rated CRITICAL with a CVSS v3.1 base score of 9.8.

Technical details

  • Root cause: the Flatastic theme deserializes attacker-controlled input via PHP’s native unserialization functionality without adequate validation (CWE-502).
  • Trigger conditions: no authentication or user interaction is required; an attacker only needs network access to a site running the vulnerable theme.
  • Attack vector: Network (AV:N), with low attack complexity and no privileges required.
  • Impact: successful exploitation can result in PHP Object Injection, which — combined with other exploitable code paths on the target (a "gadget chain") — could enable arbitrary file operations, data manipulation, or remote code execution; the vulnerability carries high impact to confidentiality, integrity, and availability.

Affected software

  • Flatastic WordPress theme (vendor: Monkeysan), versions ≤ 2.0

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 Flatastic theme to the latest version available from the vendor as soon as a fix is published; at the time of writing no specific patched version has been publicly confirmed, so verify the current theme version against the vendor’s official changelog before assuming remediation.
  • If no patch is yet available: Disable or replace the Flatastic theme on internet-facing WordPress sites, restrict access to the site via a web application firewall (WAF) with rules blocking anomalous serialized-object payloads, and monitor for unexpected PHP errors or unusual file/database activity that could indicate exploitation attempts.
  • General hardening: Ensure WordPress core, plugins, and themes are kept current, and remove unused themes/plugins to reduce the attack surface.

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/themes/flatastic/

References

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How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

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

Create Safe, Scalable Exploit Validations

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

Execute Exploit Validations

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

Drive Fast and Actionable Remediation

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.

Are you exposed?

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  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
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