CVE-2025-53328

Executive Summary

CVE-2025-53328 is a critical PHP Local File Inclusion (LFI) vulnerability discovered in the Opinion Stage Poll, Survey & Quiz Maker Plugin for WordPress, affecting all versions up to and including 19.11.0. The vulnerability stems from improper control of a filename used in a PHP include or require statement, allowing an unauthenticated attacker to include arbitrary local files from the server. This can lead to sensitive information disclosure, such as reading the wp-config.php file containing database credentials, or potentially achieving remote code execution if the attacker can upload a malicious file (e.g., via a separate file upload vulnerability) and then include it.

The vulnerability is classified under CWE-98: Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion'), though in this specific case, the attack vector is local file inclusion. The CVSS v3.1 base score is 7.5 (High), with the attack vector being network-based, low complexity, and requiring no privileges or user interaction. The impact is primarily on confidentiality (High), with no impact on integrity or availability.

As a WordPress plugin vulnerability, this issue is part of the broader WordPress ecosystem threat landscape. The plugin is widely used for creating polls, surveys, and quizzes, making it a high-value target for attackers seeking to compromise WordPress sites. No public proof-of-concept (PoC) or exploit code has been released at the time of analysis, but the vulnerability is considered exploitable due to the nature of the flaw.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress Plugin Directory and potentially third-party marketplaces. The plugin is not an NPM, PyPI, Go, or Ruby package, but it is part of the WordPress supply chain. Users who have installed the plugin via the WordPress admin dashboard or manually are at risk. The lack of a patch from the vendor (Opinion Stage) means that all installations of the plugin are currently vulnerable. Site administrators should consider removing the plugin until a fix is released.

CVSS Breakdown & Threat Level

• CVSS Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Base Score: 7.5 (High)
• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions or complex attack sequences are required.
• Privileges Required (PR): None (N) – No authentication is needed to exploit the vulnerability.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) – Sensitive files (e.g., wp-config.php) can be read.
• Integrity (I): None (N) – No file modification is possible via this vulnerability alone.
• Availability (A): None (N) – No denial of service impact.

Threat Level: High. The vulnerability is easy to exploit, requires no authentication, and can lead to the disclosure of sensitive information that may enable further attacks (e.g., database access, privilege escalation).

Deep Dive & Mechanics

The vulnerability exists in the Opinion Stage Poll, Survey & Quiz Maker Plugin (slug: social-polls-by-opinionstage). The plugin likely uses a PHP include or require statement to load template files or other resources based on user-supplied input (e.g., a page or template parameter in a URL). Due to insufficient sanitization or validation of the filename, an attacker can manipulate this parameter to include arbitrary files from the server's filesystem.

Typical vulnerable code pattern:

$template = $_GET['template'];
include( $template . '.php' );

In this scenario, an attacker could pass a path traversal sequence like ../../../../etc/passwd to read system files, or ../../../wp-config to read the WordPress configuration file.

Attack flow:

1. The attacker identifies a parameter in the plugin's URL that is used in an include or require statement.
2. The attacker crafts a request with a path traversal payload, e.g., ?page=../../../wp-config.
3. The server includes the specified file, outputting its contents (if the file is PHP, it may be executed; if not, it may be displayed as text).
4. The attacker reads sensitive data such as database credentials, salts, and keys.

Why it's dangerous: Even though this is a local file inclusion (LFI) rather than remote file inclusion (RFI), it can still lead to remote code execution if the attacker can upload a malicious file (e.g., via a separate file upload vulnerability in the same plugin or another plugin) and then include it. Additionally, reading wp-config.php provides database credentials, which can be used to access the database directly.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern and what a fix would look like.

Vulnerable code (hypothetical):

// In a plugin file, e.g., opinionstage.php
$template = $_GET['template'];
include( OPINIONSTAGE_PATH . '/templates/' . $template . '.php' );

This code directly uses user input without validation, allowing path traversal.

Patched code (recommended):

// Whitelist allowed templates
$allowed_templates = array('poll', 'survey', 'quiz');
$template = $_GET['template'];
if (in_array($template, $allowed_templates)) {
    include( OPINIONSTAGE_PATH . '/templates/' . $template . '.php' );
} else {
    // Handle error or use default template
    include( OPINIONSTAGE_PATH . '/templates/default.php' );
}

Alternatively, use basename() and realpath() to restrict the path:

$template = basename($_GET['template']);
$path = realpath(OPINIONSTAGE_PATH . '/templates/' . $template . '.php');
if ($path && strpos($path, OPINIONSTAGE_PATH . '/templates/') === 0) {
    include($path);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress installation with the Opinion Stage plugin version <= 19.11.0.
• Knowledge of the vulnerable parameter (e.g., template, page, view).

Exploitation steps:

1. Identify the vulnerable endpoint. Common patterns include:
   • http://target/wp-content/plugins/social-polls-by-opinionstage/includes/...
   • http://target/?opinionstage_action=...
2. Use a web browser or tool like curl to test for LFI:

   curl -v "http://target/wp-content/plugins/social-polls-by-opinionstage/templates.php?template=../../../wp-config"
   

3. If successful, the response will contain the contents of wp-config.php (or other files).
4. To achieve RCE, first upload a malicious PHP file (e.g., via a file upload vulnerability in the same plugin or another plugin), then include it:

   curl -v "http://target/wp-content/plugins/social-polls-by-opinionstage/templates.php?template=../../../wp-content/uploads/2025/01/shell"
   

Note: No public exploit code is available, so this is a theoretical exploitation.

Blue Team

Detection and response:

1. Monitor web server logs for suspicious path traversal patterns in request URIs, such as ../, %2e%2e%2f, or ..%2f.
2. Look for requests to plugin files with unexpected parameters (e.g., template=../../../etc/passwd).
3. Use file integrity monitoring (FIM) to detect unauthorized changes to plugin files.
4. Implement a Web Application Firewall (WAF) rule to block path traversal attempts:

   SecRule ARGS "@contains ../" "id:1001,phase:2,deny,status:403,msg:'Path Traversal Attempt'"
   

5. If exploitation is suspected, immediately isolate the affected server, rotate all credentials (database, WordPress salts), and review logs for further compromise.

Indicators of Compromise (IOCs)

• File paths accessed: /etc/passwd, /etc/shadow, /wp-config.php, /proc/self/environ
• URL patterns: ?template=../../../, ?page=../../, ?view=..%2f
• Log entries: HTTP 200 responses to requests containing ../ in parameters.
• Plugin version: social-polls-by-opinionstage version <= 19.11.0.
• Suspicious files: Unexpected files in the WordPress uploads directory (e.g., PHP shells).

Detection Engineering

YARA Rule

rule CVE_2025_53328_LFI_OpinionStage {
    meta:
        description = "Detects path traversal attempts targeting Opinion Stage plugin"
        author = "Valters IT"
        date = "2025-01-27"
        reference = "CVE-2025-53328"
    strings:
        $path_traversal = /(\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c)/ nocase
        $plugin_param = /(template|page|view|include|file)=/ nocase
    condition:
        $plugin_param and $path_traversal
}

Sigma Rule

title: CVE-2025-53328 - Opinion Stage Plugin LFI Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects path traversal attempts in HTTP requests targeting the Opinion Stage plugin
author: Valters IT
date: 2025/01/27
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains:
            - '../'
            - '..\\'
            - '%2e%2e%2f'
            - '%2e%2e%5c'
        cs-uri-query|contains|all:
            - 'opinionstage'
            - 'template='
    condition: selection
falsepositives:
    - Legitimate use of relative paths in plugin (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-53328 - Opinion Stage Plugin LFI Attempt"; flow:to_server,established; content:"opinionstage"; http_uri; content:"template="; http_uri; pcre:"/(\.\.\/|\.\.\\|%2e%2e%2f|%2e%2e%5c)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate actions:

1. Disable the plugin until a patch is released by the vendor. Go to WordPress Admin > Plugins and deactivate "Poll, Survey & Quiz Maker Plugin by Opinion Stage".
2. Implement a Web Application Firewall (WAF) rule to block path traversal patterns in URLs.
3. Review server logs for any signs of exploitation (e.g., requests containing ../ to plugin files).
4. Change all WordPress credentials (database passwords, salts, admin passwords) if exploitation is suspected.

Long-term recommendations:

1. Monitor the vendor's website (opinionstage.com) for a security update. Apply the patch as soon as it becomes available.
2. Consider alternative plugins for polls, surveys, and quizzes that have a better security track record.
3. Implement a WordPress security plugin (e.g., Wordfence, Sucuri) that can detect and block LFI attempts.
4. Regularly audit plugins for known vulnerabilities using tools like WPScan or the NVD database.

Valters IT signature: This report was generated by Valters IT DevSecOps & CTI Expert System. For questions, contact security@valters-it.com.