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CVE-2026-16940 – Unauthenticated Arbitrary File Deletion / Full Site Takeover – Custom Fields WordPr

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Summary

CVE-2026-16940 is a critical unauthenticated arbitrary file deletion vulnerability in the Custom Fields WordPress plugin in all versions before 1.5.1. The plugin fails to validate a user-supplied file path before deletion, allowing unauthenticated attackers to delete arbitrary files on the server (such as wp-config.php), which can lead to a full site takeover. It carries a maximum CVSS v3.1 base score of 10.0 (Critical).

Technical details

  • Root cause: The plugin does not validate a user-supplied file path before performing a file deletion operation (CWE-22, Improper Limitation of a Pathname to a Restricted Directory / Path Traversal).
  • Trigger conditions: An unauthenticated attacker supplies a crafted file path to the vulnerable deletion functionality; no authentication, privileges, or user interaction are required.
  • Attack vector: Network (remote, low complexity).
  • Impact: Deletion of arbitrary files on the server, including critical files such as wp-config.php. Removing such files can lead to full site takeover, with high impact to integrity and availability.

Affected software

  • Custom Fields WordPress plugin — all versions before 1.5.1.

Severity

  • CVSS v3.1 base score: 10.0 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H

Mitigation and recommended actions

  • Immediate: Update the Custom Fields WordPress plugin to version 1.5.1 or later.
  • If no patch can be applied: Deactivate and remove the plugin until it can be updated. Restrict network access to the affected WordPress site (for example, with a web application firewall rule blocking requests to the vulnerable endpoint) and monitor for unexpected deletion of core files such as wp-config.php.

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 HTTP response body: /wp-content/plugins/addify-custom-fields-for-woocommerce/

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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