1. Introduction
The is_human() Plugin for WordPress ‘type’ Parameter Command Injection vulnerability allows a remote attacker to execute arbitrary code on a web server running a vulnerable version of the plugin. This poses a High severity risk, potentially allowing complete control of the affected website and underlying infrastructure. Confidentiality, integrity, and availability may all be compromised.
2. Technical Explanation
The is_human() WordPress plugin fails to properly sanitize user input provided through the ‘type’ parameter in the ‘engine.php’ script when the ‘action’ parameter is set to ‘log-reset’. This allows an attacker to inject arbitrary PHP code, which is then executed by the server using the eval() function. An unauthenticated attacker can exploit this vulnerability remotely.
- Root cause: Insufficient input validation on the ‘type’ parameter of the ‘engine.php’ script when handling the ‘log-reset’ action.
- Exploit mechanism: An attacker sends a crafted HTTP request with malicious PHP code in the ‘type’ parameter, triggering execution via
eval(). For example, an attacker could inject code to read server files or create new administrative accounts. - Scope: WordPress websites using vulnerable versions of the is_human() plugin.
3. Detection and Assessment
To confirm vulnerability, check the installed plugin version and scan for suspicious activity in web server logs.
- Quick checks: Check the plugin version via the WordPress admin interface under ‘Plugins’ -> ‘Installed Plugins’. Look for versions prior to a patched release (if available).
- Scanning: Nessus or other vulnerability scanners may identify this issue using signature ID 47883. This is an example only, and scanner coverage varies.
- Logs and evidence: Examine web server access logs for requests containing ‘engine.php’ with the ‘action=log-reset’ parameter and unusual characters in the ‘type’ parameter.
# Example command placeholder:
# No specific command available to directly confirm exposure without accessing WordPress configuration.
4. Solution / Remediation Steps
Apply a fix by updating or removing the vulnerable plugin.
4.1 Preparation
- No services need to be stopped, but it is recommended to take the site into maintenance mode during the update process.
4.2 Implementation
- Step 1: Deactivate the ‘is_human()’ plugin through the WordPress admin interface (‘Plugins’ -> ‘Installed Plugins’).
- Step 2: Delete the ‘is_human()’ plugin files from the ‘/wp-content/plugins/’ directory via FTP or file manager.
- Step 3: If a patched version of the plugin is available, download and install it through the WordPress admin interface (‘Plugins’ -> ‘Add New’).
4.3 Config or Code Example
Before
# No specific code example available as this is a plugin vulnerability, but the insecure code involves unsanitized input being passed to eval().After
# After removing or updating the plugin, the vulnerable code is no longer present.4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence.
- Practice 2: Patch cadence – Regularly update plugins and WordPress core to address known vulnerabilities.
4.5 Automation (Optional)
# No specific automation script available for this vulnerability due to its nature. Consider using WordPress CLI tools (wp-cli) for plugin management in automated deployments.5. Verification / Validation
Confirm the fix by verifying that the vulnerable plugin is no longer installed and attempting a test exploit.
- Post-fix check: Verify that the ‘is_human()’ plugin is not listed under ‘Plugins’ -> ‘Installed Plugins’.
- Re-test: Attempt to access the ‘engine.php’ script with the ‘action=log-reset’ parameter and a malicious payload. The request should no longer execute code or return an error.
- Smoke test: Ensure that core website functionality, such as form submissions and user login, continues to work as expected.
- Monitoring: Monitor web server logs for any attempts to access the ‘engine.php’ script with suspicious parameters.
# Post-fix command and expected output:
# wp plugin list --status=inactive (should not show is_human() plugin)
6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update security baselines for WordPress plugins to include known vulnerable versions.
- Asset and patch process: Establish a regular schedule for reviewing and patching WordPress plugins, ideally within 72 hours of vulnerability disclosure.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Deactivating or deleting a plugin may break website functionality if it is essential for core features.
- Risk or side effect 2: Updating a plugin could introduce compatibility issues with other plugins or themes.
- Roll back: 1) Restore the previous WordPress files and database from backup. 2) Reinstall the original plugin version (if applicable).
8. References and Resources
- Vendor advisory or bulletin: http://www.securityfocus.com/bid/47883
- NVD or CVE entry: No specific CVE available at this time.
- Product or platform documentation relevant to the fix: https://wordpress.org/plugins/ (general WordPress plugin information)