CVE-2024-2047 Exploit & Vulnerability Analysis

The Exploit

An authenticated attacker with contributor-level access to WordPress can include and execute arbitrary PHP files on the server by manipulating the ekit_testimonial_style parameter in a request that triggers the vulnerable render_raw function.

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: target.local
Content-Type: application/x-www-form-urlencoded
Cookie: wordpress_logged_in=<valid_session>

action=ekit_testimonial_render&ekit_testimonial_style=../../../../wp-config

When this request is processed, the server will include and execute the file at wp-config.php (or any other file accessible to the web server process) because the $style parameter is directly concatenated into a require statement without path restriction. The attacker observes database credentials, authentication keys, and other sensitive constants printed in the response or reflected in error logs. If the attacker uploads a malicious PHP file to the uploads directory first, they can then use a traversal path like ../../../../wp-content/uploads/malicious to execute arbitrary code on the server.

What the Patch Did

Before

$style = isset($ekit_testimonial_style) ? sanitize_text_field($ekit_testimonial_style) : 'default';

if (is_array($testimonials) && !empty($testimonials)) {
    require Handler::get_dir() . 'style/' . $style . '.php';
}

After

$style = isset($ekit_testimonial_style) ? sanitize_text_field($ekit_testimonial_style) : 'default';
$styles = [
    'style1',
    'style2',
    'style3',
    'style4',
    'style5',
    'style6',
];

if (in_array($style, $styles) && is_array($testimonials) && !empty($testimonials)) {
    require Handler::get_dir() . 'style/' . $style . '.php';
}

The patch implements strict whitelist validation using in_array($style, $styles) before the require statement. The original code relied on sanitize_text_field(), which removes HTML tags and encodes special characters but does not prevent path traversal sequences like ../. The fix creates a hardcoded array of permitted style names and verifies that the user-supplied input matches one of those values — a capability-check pattern analogous to WordPress's in_array() checks for allowed post types or taxonomies. Only pre-defined style identifiers are now accepted; any attempt to include files outside the intended style directory is blocked.

Root Cause

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').

The ekit_testimonial_style parameter, supplied by an authenticated POST request to the AJAX handler, is received and passed through sanitize_text_field() — a function designed to prevent stored XSS and HTML injection, not path traversal. The sanitized value flows directly into a string concatenation inside a require statement:

require Handler::get_dir() . 'style/' . $style . '.php';

Because sanitize_text_field() does not filter directory traversal characters (../, ..\\), an attacker can inject relative path sequences that escape the intended style/ subdirectory. The trust boundary is crossed at the AJAX action handler: the plugin trusts that any authenticated contributor will supply only legitimate style names, but makes no cryptographic or whitelist-based check to enforce that assumption. The require language construct then executes whatever PHP file the attacker points it toward.

Why It Works

The load-bearing line is the in_array($style, $styles) check. Removing it returns the code to its vulnerable state. This single conditional gates the require, ensuring that only exact string matches to the whitelist array will proceed; a path like ../../../../wp-config will fail the in_array test and the file will not be included.

The engineer added the $styles array definition to serve as the source of truth — a hard-coded enumeration of legitimate styles that cannot be tampered with via request parameters. The additional check is_array($testimonials) && !empty($testimonials) was already present, but placing in_array first in the condition chain ensures it is evaluated before any file I/O occurs, providing early rejection. This is defense-in-depth: the original code performed zero validation on the path component, so a single whitelist check here blocks the entire class of traversal attacks. A secondary layer would be realpath() normalization, but the engineer chose the simpler and safer whitelist approach — a pattern that scales well when the set of allowed values is small and known in advance.

Hardening Checklist

• Use in_array($var, $allowed_array, true) (strict mode) for any user input that selects between a finite set of values, such as style names, page templates, or sorting orders. Never concatenate unsanitized user input into filesystem paths.

• Replace sanitize_text_field() with context-specific validation functions: use sanitize_key() for identifiers, sanitize_file_name() for file names, and whitelist checks for options that must match predefined sets. sanitize_text_field() is not a security boundary for path traversal.

• Audit all require, include, require_once, and include_once statements in AJAX and REST handlers to confirm that file paths are either static strings, come from a whitelist, or are validated with realpath() to ensure they do not escape an intended directory via is_dir() checks.

• Implement contributor-level capability checks at the AJAX entry point itself using current_user_can('edit_posts') or equivalent, and document why that role has access to file inclusion logic. If a contributor should not be able to dynamically load PHP, move the AJAX handler to require 'manage_options'.

• Log all file inclusion attempts (parameter value, resolved path, inclusion result) to catch exploitation attempts during incident response. WordPress does not do this by default; use a custom filter on wp_ajax_* actions to record the $_POST payload before the handler runs.

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-2047