Critical ACF Extended Flaw (CVE-2025-13486, CVSS 9.8) Allows Unauthenticated RCE on 100K WordPress Sites

Estimated reading time: 7 minutes

  • Critical RCE vulnerability in Advanced Custom Fields: Extended plugin (CVE-2025-13486).
  • Unauthenticated attackers can execute arbitrary code remotely.
  • Update to version 0.9.2 immediately to remediate the flaw.
  • Consider implementing WAF rules and regular vulnerability scanning.
  • PurpleOps offers services to help protect against such vulnerabilities.

Table of Contents:

Technical Breakdown of CVE-2025-13486

A critical security vulnerability, identified as CVE-2025-13486, has been discovered in the “Advanced Custom Fields: Extended” plugin for WordPress. This flaw carries a CVSS score of 9.8, indicating near-maximum severity. The vulnerability allows unauthenticated attackers to execute arbitrary code remotely on affected websites, potentially granting them full control. With over 100,000 installations, the impact of this vulnerability is significant.

The flaw was discovered by security researcher dudekmar through the Wordfence Bug Bounty Program, earning them a reward of $4,290.00 due to the severity and quality of the report.

The vulnerability exists within the prepare_form() function of the acfe_module_form_front_render class in the Advanced Custom Fields: Extended plugin. This class is responsible for rendering forms on the frontend of WordPress websites.

The root cause of the issue lies in the plugin’s handling of user input during the form rendering process. Specifically, the code utilizes call_user_func_array, a PHP function that calls a specified callback with an array of parameters. The critical issue is that the data used by this function is directly supplied by the user without proper validation.

The technical analysis revealed that “the function used to render the form is defined using the ‘form[render]’ parameter retrieved from user input, and the data passed to the function is retrieved from the ‘form’ parameter, which is also supplied via user input.” This lack of input validation creates a direct pathway for attackers to inject arbitrary code.

The report further clarifies that “there is no restriction on the function call, which means that the attacker can call an arbitrary PHP function through the ‘form[render]’ parameter… making arbitrary code injection possible.” This is the core of the unauthenticated Remote Code Execution (RCE) vulnerability.

Implications of the RCE Vulnerability

The implications of CVE-2025-13486 are severe. Because it is an unauthenticated RCE flaw, an attacker does not need to be logged in or have any prior access to the WordPress site to exploit it. This significantly lowers the barrier to entry for malicious actors.

Researchers have demonstrated how this vulnerability can be leveraged for privilege escalation. For example, an attacker could use the wp_insert_user() function to create a new administrator account. Once administrative access is obtained, the attacker effectively owns the entire website.

As with all remote code execution vulnerabilities, this can lead to complete site compromise through the deployment of webshells and other techniques. An attacker could steal sensitive data, deface the website, install malware, or use the compromised server as a launching point for further attacks. This highlights the need for robust breach detection and immediate remediation.

Warning symbol over WordPress site code highlighting RCE flaw

Remediation and Mitigation

The development team behind Advanced Custom Fields: Extended has addressed this vulnerability in version 0.9.2. The fix involves completely removing the user input and call_user_func_array() function-based rendering from the prepare_form() function.

Administrators utilizing the Advanced Custom Fields: Extended plugin are urged to verify their installation version immediately. Updating to the latest patched version, 0.9.2, is crucial to protect against this critical vulnerability.

Practical Takeaways and Actionable Advice

For Technical Readers (System Administrators, Security Engineers):

  • Immediate Patching: Prioritize updating the Advanced Custom Fields: Extended plugin to version 0.9.2 on all WordPress installations.
  • Web Application Firewall (WAF): Consider implementing or updating WAF rules to detect and block potential exploitation attempts targeting this vulnerability.
  • Regular Vulnerability Scanning: Incorporate regular vulnerability scanning into your security routine to identify and address potential weaknesses promptly. Consider using a cyber threat intelligence platform to stay ahead of emerging threats.
  • Code Review: If you develop or maintain custom WordPress plugins, ensure thorough code reviews are conducted to identify and prevent similar vulnerabilities.

For Non-Technical Readers (Business Leaders, Website Owners):

  • Communicate with your IT Team: Ensure your IT team or web developers are aware of this vulnerability and have taken steps to update the Advanced Custom Fields: Extended plugin.
  • Verify Plugin Versions: Confirm that all WordPress plugins are up-to-date. Outdated plugins are a common entry point for attackers.
  • Understand the Risks: Be aware of the potential consequences of a compromised website, including data breaches, financial losses, and reputational damage.
  • Invest in Security: Allocate resources to cybersecurity measures, such as regular security audits and penetration testing, to protect your website and business. Consider supply-chain risk monitoring to ensure third-party components are secure.

Relevance to PurpleOps Services

This vulnerability underscores the importance of several cybersecurity services offered by PurpleOps:

  • Vulnerability Management: PurpleOps provides comprehensive vulnerability management services, including identifying, assessing, and remediating vulnerabilities in web applications and infrastructure.
  • Penetration Testing: Our penetration testing services simulate real-world attacks to identify weaknesses in your security posture, allowing you to proactively address vulnerabilities like CVE-2025-13486. More information on this topic can be found here: https://www.purple-ops.io/penetration-testing
  • Red Team Operations: PurpleOps’s red team operations provide a more advanced level of security testing, simulating sophisticated attacker tactics to identify and exploit vulnerabilities that may be missed by traditional methods. Additional details can be found here: https://www.purple-ops.io/red-team-operations
  • Cyber Threat Intelligence: Leveraging a cyber threat intelligence platform, PurpleOps monitors emerging threats and vulnerabilities, providing clients with timely and actionable intelligence to protect against attacks. We also offer real-time ransomware intelligence to help you understand your risk profile.
  • Supply Chain Information Security: Understanding the risks associated with third-party software, like WordPress plugins, is critical. PurpleOps provides supply-chain risk monitoring to help you assess and manage the security of your vendors and partners. Learn more here: https://www.purple-ops.io/supply-chain-information-security
  • Dark Web Monitoring: PurpleOps can monitor the dark web monitoring service and underground forum intelligence for mentions of your company, brand, or infrastructure, providing early warning of potential threats. We also provide brand leak alerting to identify leaked credentials or sensitive information.
  • Protect Ransomware: A compromised WordPress site can easily lead to a ransomware infection. PurpleOps offers services to help you protect ransomware attacks, including vulnerability management, security awareness training, and incident response planning. More information can be found here: https://www.purple-ops.io/protect-ransomware
  • Breach Detection: With proactive breach detection, PurpleOps is able to discover threats faster than others.

By leveraging services like these, organizations can significantly reduce their risk of falling victim to vulnerabilities like CVE-2025-13486 and other cyber threats. Moreover, our telegram threat monitoring services can provide additional insights into emerging threats and attacker communications.

Call to Action

Protect your organization from critical vulnerabilities like CVE-2025-13486. Explore PurpleOps’s comprehensive suite of cybersecurity services, including vulnerability management, penetration testing, and cyber threat intelligence, to strengthen your security posture. Visit https://www.purple-ops.io/services/ for more information. Contact us to discuss your specific security needs and how we can help you stay protected: https://www.purple-ops.io/platform/

FAQ

Q: What is CVE-2025-13486?

A: CVE-2025-13486 is a critical Remote Code Execution (RCE) vulnerability in the Advanced Custom Fields: Extended plugin for WordPress.

Q: What is the CVSS score of this vulnerability?

A: The vulnerability has a CVSS score of 9.8, indicating near-maximum severity.

Q: How can I fix this vulnerability?

A: Update the Advanced Custom Fields: Extended plugin to version 0.9.2 or later.

Q: Does PurpleOps offer services to help with this type of vulnerability?

A: Yes, PurpleOps offers vulnerability management, penetration testing, cyber threat intelligence, and other services to help protect against vulnerabilities like CVE-2025-13486.