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Quick Fix for CVE-2023-5561 WordPress Bug: Secure Your Site Today

December 19, 2023


The CVE-2023-5561 vulnerability in WordPress has raised concerns for website owners and developers. This security flaw poses significant risks, including the potential for unauthorized access and data compromise. Understanding and resolving this issue is critical for maintaining the integrity and security of WordPress sites.

Understanding CVE-2023-5561

CVE-2023-5561 is a vulnerability within WordPress that fails to restrict searchable user fields via the REST API. This allows unauthenticated attackers to discern the email addresses of users who have published public posts on an affected website​​. Additionally, the Popup Builder plugin through version 4.1.15 doesn't properly sanitize some settings, enabling stored Cross-Site Scripting attacks by high privilege users​​. The bug has a CVSS base score of 5.3, indicating a medium severity level​​.

Impact on WordPress Sites

The primary risk involves a threat actor exploiting a PHP object injection vulnerability present in other plugins or themes, potentially leading to arbitrary code execution and control over the targeted site​​. This vulnerability is particularly concerning in multisite installations and when combined with specific plugins.

Resolution Steps

  1. Update to WordPress 6.4.2: WordPress released version 6.4.2, patching the critical security flaw​​. Ensuring your WordPress installation is updated to this version is the first and most crucial step in addressing CVE-2023-5561.
  2. Review Plugin and Theme Security: The vulnerability can be exacerbated by other plugins or themes. Review and update all plugins and themes to their latest versions. Remove any unused or unsupported plugins and themes as a precautionary measure.
  3. Modify Code Where Necessary: Developers should replace any use of the unserialize function in their code with safer alternatives like JSON encoding/decoding using the json_encode and json_decode PHP functions to prevent object injection vulnerabilities​​.
  4. Regular Security Audits: Conduct regular security audits of your WordPress site. Use tools like WPScan to identify potential vulnerabilities and address them proactively.
  5. Implement Security Best Practices: Employ general WordPress security best practices, such as strong passwords, limited login attempts, and the use of security plugins.


Resolving the CVE-2023-5561 vulnerability is crucial for the security and integrity of WordPress sites. By following these steps, website owners and developers can mitigate the risks associated with this bug and ensure a secure environment for their users.