CVE-2025-8905

Executive Summary

CVE-2025-8905 is a critical Remote Code Execution (RCE) vulnerability in the Inpersttion For Theme WordPress plugin, affecting all versions up to and including 1.0. The flaw resides in the theme_section_shortcode() function, which fails to restrict the functions that can be called by authenticated users. This allows attackers with at least Contributor-level access to execute arbitrary PHP functions on the server, albeit without the ability to supply user-controlled parameters. The vulnerability is currently unpatched, and no public exploit code or proof-of-concept has been released. Given the WordPress ecosystem context, this poses a significant risk to sites using this plugin, as it can lead to full site compromise, data exfiltration, or further lateral movement within the hosting environment.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is not distributed via NPM, PyPI, Go, or Ruby registries. However, it is available through the official WordPress plugin repository and potentially third-party marketplaces. Users should verify the integrity of the plugin file and consider removing it until a patch is available.

CVSS Breakdown & Threat Level

• CVSS Score: 6.3 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – Contributor-level access
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: Medium. While the CVSS score is moderate, the potential for RCE in a WordPress context elevates the risk. The requirement for authenticated access reduces the attack surface, but once an attacker gains Contributor-level credentials (e.g., via phishing or weak passwords), exploitation is straightforward.

Deep Dive & Mechanics

The vulnerability exists in the theme_section_shortcode() function, which is registered as a WordPress shortcode. This function is intended to render dynamic content based on user input. However, due to insufficient input validation and lack of a whitelist for allowed functions, an attacker can call arbitrary PHP functions.

Root Cause: The plugin uses a pattern similar to call_user_func() or call_user_func_array() without restricting the function name. For example, the code might look like:

function theme_section_shortcode($atts) {
    $function = $atts['function'];
    return call_user_func($function);
}

This allows an attacker to specify any PHP function name in the shortcode attributes. Since no parameters are passed, the attacker is limited to functions that require no arguments, such as phpinfo(), get_defined_functions(), or wp_get_current_user(). However, this can still be leveraged to enumerate the environment, leak sensitive information, or trigger other vulnerabilities.

Exploitation Scenario:

1. An attacker with Contributor-level access creates a new post or page.
2. The attacker inserts a shortcode like: [theme_section function="phpinfo"]
3. When the post is rendered, the phpinfo() function executes, revealing server configuration details.
4. The attacker can then use this information to plan further attacks, such as exploiting other vulnerabilities or using disclosed credentials.

Vulnerable vs. Patched Code

Vulnerable Code (version 1.0):

function theme_section_shortcode($atts) {
    $function = $atts['function'];
    return call_user_func($function);
}
add_shortcode('theme_section', 'theme_section_shortcode');

Patched Code (hypothetical):

function theme_section_shortcode($atts) {
    $allowed_functions = array('safe_function1', 'safe_function2');
    $function = $atts['function'];
    if (in_array($function, $allowed_functions)) {
        return call_user_func($function);
    } else {
        return 'Function not allowed.';
    }
}
add_shortcode('theme_section', 'theme_section_shortcode');

The patched version implements a whitelist of allowed functions, preventing arbitrary code execution.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress instance with the Inpersttion For Theme plugin (version 1.0) installed and activated.
• A user account with Contributor-level privileges or higher.

Steps:

1. Log in to WordPress as a Contributor.
2. Create a new post or page.
3. In the content editor, insert the following shortcode:

   [theme_section function="phpinfo"]
   

4. Publish or preview the post.
5. Observe that the phpinfo() output is displayed, confirming RCE.

Advanced Exploitation:

• Use get_defined_functions to list all available functions.
• Use wp_get_current_user to retrieve user data.
• Use file_get_contents (if allowed) to read arbitrary files, but note that this function requires a parameter, so it may not work directly.

Blue Team

Detection:

• Monitor for posts or pages containing shortcodes with unusual function names.
• Look for HTTP requests to wp-admin/post.php or wp-admin/admin-ajax.php with parameters like function=phpinfo.
• Check server logs for unexpected function calls or errors.

Hunting:

• Search the WordPress database for posts containing [theme_section in the post_content column.
• Use the following SQL query:

  SELECT * FROM wp_posts WHERE post_content LIKE '%[theme_section%';
  

Containment:

• Immediately disable or remove the Inpersttion For Theme plugin.
• Revoke Contributor-level access for suspicious accounts.
• Review and rotate all WordPress credentials.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/inpersttion-for-theme/inpersttion-for-theme.php
• Shortcode pattern: [theme_section function="<function_name>"]
• HTTP request parameter: function=phpinfo or similar
• Log entry: PHP warning or error related to call_user_func with unexpected function names
• Database entry: Posts containing [theme_section in post_content

Detection Engineering

YARA Rule

rule CVE_2025_8905_Inpersttion_RCE {
    meta:
        description = "Detects Inpersttion For Theme plugin vulnerable to RCE"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-8905"
    strings:
        $plugin_file = "inpersttion-for-theme.php"
        $vuln_func = "theme_section_shortcode"
        $call_user = "call_user_func"
    condition:
        $plugin_file and $vuln_func and $call_user
}

Sigma Rule

title: CVE-2025-8905 - Inpersttion For Theme RCE
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts of CVE-2025-8905 via shortcode injection
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains: 'function=phpinfo'
    condition: selection
falsepositives:
    - Legitimate use of phpinfo by administrators
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-8905 - Inpersttion For Theme RCE Attempt"; flow:to_server,established; content:"function=phpinfo"; http_uri; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete the Inpersttion For Theme plugin from all WordPress installations.
2. Audit user accounts: Review all users with Contributor-level access or higher. Remove or downgrade suspicious accounts.
3. Scan for compromise: Use the provided YARA and Sigma rules to scan for existing exploitation.

Long-term Mitigation:

• Patch: Since no official patch is available, consider forking the plugin and implementing a whitelist of allowed functions as shown in the patched code example.
• Monitor: Subscribe to WordPress security advisories and the CVE feed for updates.
• Principle of Least Privilege: Restrict user roles and capabilities. Avoid granting Contributor-level access to untrusted users.
• Web Application Firewall (WAF): Deploy a WAF rule to block shortcodes containing suspicious function names.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.