Unauthenticated PHP Object Injection Flaw Found in CleanSkin Plugin
A critical vulnerability in the CleanSkin WordPress plugin allows attackers to inject malicious code without logging in.
Key points
- CVE-2026-42723 is rated critical with a CVSS score of 9.8 by the National Vulnerability Database.
- The flaw affects versions of the AncoraThemes CleanSkin plugin up to and including version 1.5.0.
- The vulnerability involves unauthenticated PHP object injection, classified under CWE-502.
The National Vulnerability Database has recorded a critical security flaw in the CleanSkin WordPress plugin, identified as CVE-2026-42723. This vulnerability allows unauthenticated attackers to exploit the plugin without needing valid credentials or user access to the website backend.
At a glance
- CVE
- CVE-2026-42723
- Product
- AncoraThemes CleanSkin
- CVSS
- 9.8 Critical
- Weakness
- insecure deserialization
- Exploited
- No known exploitation
The issue stems from improper handling of PHP objects, enabling remote code execution through object injection. The National Vulnerability Database assigns the flaw a CVSS score of 9.8, marking it as critical due to the ease of exploitation and severe potential impact on affected systems.
Context and Background
The vulnerability is categorized under CWE-502, which describes the improper restriction of XML external entity references or similar injection weaknesses that allow attackers to manipulate object deserialization processes. In this specific case, the flaw permits the injection of malicious PHP objects directly into the application logic.
According to the NVD record, the weakness exists in the CleanSkin plugin developed by AncoraThemes. The plugin is designed to improve website performance by minifying and caching CSS and JavaScript files, but the security flaw compromises the integrity of the server hosting the site.
Who Is Affected
The vulnerability impacts all installations of the AncoraThemes CleanSkin plugin running version 1.5.0 or earlier. Any WordPress site using these versions is potentially exposed to remote exploitation. Website administrators must verify their current plugin version immediately to determine if their environment is within the affected range.
Sites that have not updated to a patched version beyond 1.5.0 remain vulnerable to unauthenticated attacks. The lack of authentication requirements for exploitation means that automated scanning tools or opportunistic attackers can target these systems without prior interaction or social engineering efforts.
What should you do?
Security teams should audit their WordPress installations to identify any sites running the affected versions of the CleanSkin plugin. Administrators should check for any recent updates from the vendor that address CVE-2026-42723. If no update is available, consider disabling the plugin temporarily to mitigate risk.
Monitor server logs for unusual activity or signs of unauthorized code execution. Ensure that web application firewalls are configured to detect and block suspicious requests targeting the plugin’s endpoints. Review access controls to limit exposure to public-facing interfaces.
Background: Social engineering
Look for urgency, secrecy, and deviation from standard channels. Verify identity through a separate, known communication path before acting. Isolate suspicious interactions immediately to prevent lateral movement within your network environment.
Read the full guide: Social Engineering Warning Signs and How to Respond
What to do and how to stay safe: CleanSkin
- Check your WordPress plugin list for CleanSkin versions 1.5.0 or older and disable them if no patch is available.
- Monitor server logs for unexpected PHP execution or unusual traffic patterns targeting the plugin.
- Verify that your web application firewall rules are updated to block known exploitation attempts for this CVE.
- Contact the vendor, AncoraThemes, to inquire about the status of a security patch for CVE-2026-42723.
Step-by-step guide: Risk Based Vulnerability Management: Prioritize Fixes by Actual Threat
General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is CVE-2026-42723?
CVE-2026-42723 is a critical vulnerability in the CleanSkin WordPress plugin that allows unauthenticated PHP object injection.
Which versions of CleanSkin are affected?
All versions of the AncoraThemes CleanSkin plugin up to and including version 1.5.0 are affected by this vulnerability.
How severe is this vulnerability?
The National Vulnerability Database rates CVE-2026-42723 as critical with a CVSS score of 9.8.
