Security vulnerabilities in WordPress plugins are a known theme, but sometimes they land in surprising places. CVE-2022-3834 is one of those: it hit the popular Google Forms WordPress plugin (through version .95) and lets even admins with limited rights plant persistent cross-site scripting (XSS) payloads—potentially taking over a WordPress site from the inside.

This post will break down how the vulnerability works, provide code examples for the exploit, and share how you can test or secure your site. You’ll find links to the original advisory and extra context for clarity.

Summary of the Vulnerability

CVE-2022-3834 was filed after researchers discovered the *Google Forms WordPress plugin* did not properly sanitize or escape certain plugin settings. This made it possible for high-privileged WordPress users (admins or super admins, depending on configuration) to store malicious JavaScript as settings for the plugin.

This is super serious in places like a WordPress Multisite setup, where even site admins do *not* have the unfiltered_html capability for security. They’re supposed to be safe from executing JavaScript, but this bug bypassed that safety net.

Even admins *without* full privileges can plant JavaScript payloads.

- Attackers could hijack new admin sessions, deface the site, or steal sensitive data—even across different subsites.

Original References

- NIST CVE Entry for CVE-2022-3834
- WPScan Advisory
- Plugin Download Page *(for checking your version)*

Technical Details: Where is the Bug?

The vulnerability sits inside the plugin’s settings management. When plugin settings are saved, the input isn’t always cleaned. For example, if the plugin lets admins add a custom message or code block, it treats the input as safe and puts it straight into the WordPress database. Later, when this setting is shown on the WordPress dashboard or on public pages, it’s output without escaping—triggering any malicious script.

Key vulnerable code flow

if( isset( $_POST['custom_message'] ) ) {
    // This is how the setting might be stored (version <= .95)
    update_option('gform_custom_message', $_POST['custom_message']);
}

// Later, this is displayed somewhere:
echo get_option('gform_custom_message');

*(Note: This is a simplified example inspired by the actual plugin’s code pattern.)*

Exploitation Example

Suppose an attacker is an administrator on a WordPress Multisite, but *does not* have the unfiltered_html privilege.

`html

Save the settings.

4. Anyone who visits the part of the WordPress dashboard or website where this setting is displayed (could be other admins, super admins, or visitors) will instantly run the script.

*Real-world impact?* Things like session hijacking, stealing cookies, redirecting users, or planting persistent backdoors in the WordPress backend.

How to Test If You’re Vulnerable

1. Check your plugin version: Go to *Plugins → Installed Plugins* and make sure you are NOT running *Google Forms* plugin version .95 or lower.
2. Try injecting harmless XSS payloads: If you control a test site, put <img src=x onerror=alert(1)> into custom message fields in the plugin settings. If the alert pops up later, you’re vulnerable.

Fix & Recommendations

- Upgrade Immediately: The plugin developer fixed this issue in version .96. Just update.
- Never trust input: Plugin developers should *always* sanitize and escape user input before saving or outputting. Use esc_html() or sanitize_text_field() as appropriate.

Example secure code

if( isset( $_POST['custom_message'] ) ) {
    $safe_input = sanitize_text_field($_POST['custom_message']);
    update_option('gform_custom_message', $safe_input);
}

// Later, when displaying:
echo esc_html(get_option('gform_custom_message'));

- Use security plugins: Consider using something like Wordfence to get alerts for plugin vulnerabilities.

Conclusion

*CVEs* like CVE-2022-3834 remind us that even trusted plugins can have dangerous bugs—bugs that let insiders escalate attacks or break the security separations multisite relies on. If you run WordPress and use this plugin, patch fast, and always keep an eye on plugin security feeds.

Have questions or want a code audit? Drop a comment or reach out to a WordPress security pro.

Timeline

Published on: 11/28/2022 14:15:00 UTC
Last modified on: 11/30/2022 03:50:00 UTC