WordPress users should be aware of a vulnerability present in the Contact Form 7 plugin, which is widely used for creating and managing contact forms on websites. This vulnerability is present in versions up to and including 5.8.3, and it allows for arbitrary file uploads by authenticated attackers with editor-level capabilities or higher. In most cases, this will not lead directly to remote code execution due to the htaccess configuration. However, when combined with another vulnerability, such as local file inclusion, the consequences can be more severe.

Vulnerability Details

The two primary causes of this vulnerability are insufficient file type validation in the 'validate' function and insufficient blocklisting on the 'wpcf7_antiscript_file_name' function. This essentially means that the plugin does not do a proper check to ensure that only files of a certain type can be uploaded, potentially allowing for the upload of malicious files.

Here's an example of the problematic code in the 'validate' function

function validate($value, $options = array()) {
  if (!wpcf7_is_file_path($value)) {
    return false;
  }

  $value = sanitize_file_name($value);

  if (wpcf7_antiscript_file_name($value)) {
    return false;
  }
}

As you can see, the file name is sanitized, but there is no validation based on the file type.

Mitigation

It is essential for WordPress users to keep their plugins up-to-date, and developers should release fixes for these vulnerabilities as soon as possible. Until such a fix is available for Contact Form 7, website owners using this plugin should consider applying the following mitigation techniques:

1. Implement proper file type validation and blocklisting in the 'validate' and 'wpcf7_antiscript_file_name' functions. This will ensure that only files with specific extensions can be uploaded.

Change the default .htaccess configuration to prevent remote code execution for uploaded files.

3. Restrict plugin access to trusted users with editor-level capabilities or higher, reducing the potential attack surface.

Original References

To further understand the vulnerability, readers can refer to the original source that disclosed the vulnerability:

- Contact Form 7 Vulnerability Details and Mitigation Tips

Conclusion

This vulnerability in the Contact Form 7 plugin for WordPress serves as an important reminder for website owners to keep their plugins up-to-date and pay close attention to security best practices. By implementing the suggested mitigation techniques and staying informed about potential vulnerabilities, you can reduce the risk of security breaches and keep your WordPress site safe and secure.

Timeline

Published on: 12/01/2023 11:15:08 UTC
Last modified on: 12/06/2023 20:56:48 UTC