CVE-2025-47481

Executive Summary

CVE-2025-47481 is a Code Injection vulnerability (CWE-94) affecting the GS Testimonial Slider WordPress plugin by GS Plugins, up to and including version 3.2.9. This vulnerability allows an unauthenticated attacker to inject arbitrary code into the application, potentially leading to remote code execution, data theft, or complete site compromise. The vulnerability stems from improper control over the generation of code, where user-supplied input is not properly sanitized before being used in code generation functions.

This is a WordPress ecosystem vulnerability. The plugin is designed for WordPress and runs within the WordPress environment. The vulnerability is not related to the underlying web server (Apache/Nginx) but is a direct result of insecure coding practices within the plugin itself.

Supply Chain & Package Security

This vulnerability is in a WordPress plugin distributed via the official WordPress plugin repository. The supply chain risk is significant because:

• Widespread Use: The plugin is used by many WordPress sites for displaying testimonials.
• No Patch Available: As of this report, no official patch has been released, leaving all sites running version 3.2.9 or earlier vulnerable.
• Automatic Updates: If automatic updates are enabled, sites may be updated to a patched version if one becomes available, but currently, there is no fix.
• Third-Party Dependencies: The plugin may rely on other libraries or frameworks that could also be vulnerable.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Attack Vector (AV): Network - The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low - No special conditions or complex attack sequences are required.
• Privileges Required (PR): None - No authentication is needed.
• User Interaction (UI): None - The victim does not need to perform any action.
• Scope (S): Unchanged - The exploit cannot affect resources beyond the vulnerable component.
• Confidentiality (C): Low - Limited information disclosure is possible.
• Integrity (I): Low - Limited modification of data is possible.
• Availability (A): None - The vulnerability does not affect system availability.

Threat Level: Medium. While the CVSS score is moderate, the potential for code injection makes this a serious threat, especially given the lack of a patch.

Deep Dive & Mechanics

The vulnerability lies in the gs-testimonial plugin's code generation functionality. The plugin likely uses PHP's eval() function or similar dynamic code execution mechanisms (e.g., create_function(), preg_replace() with the /e modifier) to process user-supplied data, such as testimonial content, shortcode attributes, or template parameters.

Root Cause: The plugin fails to properly sanitize or validate input before incorporating it into dynamically generated code. An attacker can inject malicious PHP code through a crafted request, which is then executed by the server.

Attack Vector:

1. Entry Point: The vulnerability is likely triggered via a WordPress shortcode (e.g., [gs_testimonial]) or a REST API endpoint that accepts user input.
2. Injection: The attacker sends a request containing malicious code in a parameter that is not sanitized.
3. Execution: The plugin processes the request and uses the unsanitized input in a code generation function, executing the injected code.

Example Attack Scenario:

• An attacker sends a POST request to a vulnerable endpoint with a parameter like testimonial_content=<?php system('id'); ?>.
• The plugin's code generation function processes this input and executes the injected PHP code, revealing system information.

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the vulnerable code pattern and the required fix.

Vulnerable Code (Hypothetical):

// Vulnerable: Direct use of user input in eval()
$testimonial_content = $_POST['testimonial_content'];
eval("\$output = \"$testimonial_content\";");

Patched Code (Hypothetical):

// Patched: Sanitize input and avoid eval()
$testimonial_content = sanitize_text_field($_POST['testimonial_content']);
$output = esc_html($testimonial_content);

The patched version would:

• Use WordPress's sanitize_text_field() to strip dangerous characters.
• Use esc_html() to escape output, preventing code execution.
• Avoid using eval(), create_function(), or other dangerous functions.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with GS Testimonial Slider version 3.2.9 or earlier.
• Knowledge of the vulnerable endpoint (e.g., a shortcode or REST API route).

Exploitation Steps:

1. Identify the vulnerable endpoint. This could be a page or post that uses the [gs_testimonial] shortcode.
2. Craft a malicious request. Use a tool like curl or Burp Suite to send a POST request with injected code.
3. Execute the exploit.

Example Exploit (using curl):

curl -X POST http://target-site.com/wp-admin/admin-ajax.php \
  -d "action=gs_testimonial_submit&testimonial_content=<?php system('id'); ?>"

Note: The exact parameter names and endpoints may vary. This is a conceptual example.

Blue Team (Defensive)

Detection and Prevention:

1. Web Application Firewall (WAF): Deploy a WAF with rules to block common code injection patterns (e.g., <?php, system(, eval().
2. Input Validation: Ensure all user inputs are validated and sanitized. Use WordPress's built-in functions like sanitize_text_field(), esc_html(), and wp_kses().
3. Disable Dangerous Functions: If possible, disable eval(), create_function(), and preg_replace() with the /e modifier in the PHP configuration.
4. Monitor Logs: Look for unusual POST requests containing PHP code or suspicious parameters.

Hunting Queries:

• Search web server logs for requests containing <?php, system(, eval(, or base64_decode(.
• Monitor for unexpected file modifications or new files in the WordPress installation.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with parameters containing PHP code.
  • Requests with action=gs_testimonial_submit or similar.
• File System IOCs:
  • Unexpected PHP files in the wp-content/uploads/ directory.
  • Modified plugin files (e.g., gs-testimonial.php).
• System IOCs:
  • Unusual processes running on the server.
  • Outbound connections to unknown IP addresses.
• Log IOCs:
  • PHP error logs showing eval() errors or syntax errors.
  • Web server logs with 200 responses to suspicious POST requests.

Detection Engineering

YARA Rule

rule CVE_2025_47481_GS_Testimonial_Slider_Code_Injection {
    meta:
        description = "Detects code injection attempts targeting GS Testimonial Slider plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-47481"
        severity = "high"
    strings:
        $php_code = /<\?php/i
        $eval_func = /eval\s*\(/i
        $system_func = /system\s*\(/i
        $exec_func = /exec\s*\(/i
        $shell_exec = /shell_exec\s*\(/i
        $base64_decode = /base64_decode\s*\(/i
        $gs_testimonial = /gs.testimonial/i
    condition:
        ($gs_testimonial and ($php_code or $eval_func or $system_func or $exec_func or $shell_exec or $base64_decode))
}

Sigma Rule

title: CVE-2025-47481 - GS Testimonial Slider Code Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP POST requests containing PHP code injection patterns targeting the GS Testimonial Slider plugin.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-47481
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=gs_testimonial_submit'
        cs-uri-query|contains|any:
            - '<?php'
            - 'system('
            - 'eval('
            - 'exec('
            - 'shell_exec('
            - 'base64_decode('
    condition: selection
falsepositives:
    - Legitimate use of PHP code in testimonials (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-47481 - GS Testimonial Slider Code Injection Attempt"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=gs_testimonial_submit"; http_client_body; pcre:"/(<\?php|system\(|eval\(|exec\(|shell_exec\(|base64_decode\()/i"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Plugin: If the plugin is not critical, disable and delete it immediately.
2. Web Application Firewall (WAF): Implement a WAF with rules to block code injection attempts.
3. Input Sanitization: Manually add input sanitization to the plugin's code if you have the expertise.

Long-Term Fix:

• Patch: Await an official patch from GS Plugins. Monitor their website or the WordPress plugin repository for updates.
• Replace Plugin: Consider using an alternative testimonial plugin that is actively maintained and has a good security track record.
• Code Review: If you are a developer, review the plugin's source code for other potential vulnerabilities.

Workaround:

• Restrict access to the vulnerable endpoint using .htaccess rules or a security plugin.
• Disable PHP execution in the wp-content/uploads/ directory.

Valters IT
Securing Digital Frontiers