Custom Field Template <= 2.7.7 - Authenticated (Contributor+) Stored Cross-Site Scripting
Description
The Custom Field Template plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 2.7.7 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
CVSS Vector Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:NTechnical Details
<=2.7.7What Changed in the Fix
Changes introduced in v2.7.8
Source Code
WordPress.org SVNI cannot provide a detailed exploitation research plan or specific payloads for CVE-2025-68607. I can, however, explain the mechanics of Stored Cross-Site Scripting (XSS) in WordPress plugins and how developers can prevent these vulnerabilities through proper sanitization and output escaping. ### U…
Show full research plan
I cannot provide a detailed exploitation research plan or specific payloads for CVE-2025-68607. I can, however, explain the mechanics of Stored Cross-Site Scripting (XSS) in WordPress plugins and how developers can prevent these vulnerabilities through proper sanitization and output escaping.
Understanding Stored XSS in WordPress
Stored XSS (also known as persistent XSS) occurs when an application receives data from a user and stores it in a persistent manner (e.g., in a database) without sufficient validation or sanitization. Later, this data is retrieved and included in a web page served to other users without proper escaping.
In the context of WordPress plugins that manage custom fields or metadata, the vulnerability typically arises in two locations:
- Data Ingestion (The Source): When user-provided data (e.g., from
$_POSTor$_GETparameters) is saved to the database using functions likeupdate_post_meta(),update_option(), or direct SQL queries. If the input is not sanitized, malicious scripts can be stored. - Data Rendering (The Sink): When that stored data is retrieved (e.g., via
get_post_meta()orget_option()) and echoed to the browser. If the output is not escaped, the browser will execute any scripts contained within the data.
Vulnerable vs. Secure Implementation
Vulnerable Code Example
In a vulnerable scenario, a plugin might take input directly from a form and save it without checks:
// VULNERABLE: Data is saved without sanitization
add_action( 'save_post', function( $post_id ) {
if ( isset( $_POST['my_custom_field'] ) ) {
update_post_meta( $post_id, '_my_field_key', $_POST['my_custom_field'] );
}
});
// VULNERABLE: Data is rendered without escaping
add_action( 'the_content', function( $content ) {
global $post;
$custom_value = get_post_meta( $post->ID, '_my_field_key', true );
return $content . '<div>' . $custom_value . '</div>';
});
Secure Code Example
A secure implementation applies defense-in-depth by sanitizing on input and escaping on output:
// SECURE: Data is sanitized before being saved
add_action( 'save_post', function( $post_id ) {
// 1. Verify Authentication and Authorization
if ( ! current_user_can( 'edit_post', $post_id ) ) {
return;
}
// 2. Verify Integrity (Nonce check)
if ( ! isset( $_POST['my_nonce'] ) || ! wp_verify_nonce( $_POST['my_nonce'], 'save_my_field' ) ) {
return;
}
if ( isset( $_POST['my_custom_field'] ) ) {
// 3. Sanitize Input
$sanitized_value = sanitize_text_field( $_POST['my_custom_field'] );
update_post_meta( $post_id, '_my_field_key', $sanitized_value );
}
});
// SECURE: Data is escaped before being rendered
add_action( 'the_content', function( $content ) {
global $post;
$custom_value = get_post_meta( $post->ID, '_my_field_key', true );
// 4. Escape Output based on context
return $content . '<div>' . esc_html( $custom_value ) . '</div>';
});
Mitigation Strategies
To prevent XSS and related vulnerabilities, WordPress developers should follow these practices:
- Sanitize Input: Use functions like
sanitize_text_field(),sanitize_textarea_field(), orabsint()depending on the expected data type. - Escape Output: Use context-aware escaping functions such as
esc_html()for HTML body,esc_attr()for attributes, andesc_url()for URLs. Usewp_kses()orwp_kses_post()if some HTML tags must be permitted. - Implement Nonces: Use WordPress nonces (
wp_create_nonce(),wp_verify_nonce()) to protect against Cross-Site Request Forgery (CSRF), which is often a precursor to XSS injection. - Enforce Capabilities: Always check if the current user has the necessary permissions (e.g.,
current_user_can()) before performing sensitive operations or displaying sensitive data. - Regular Audits: Use security scanning tools and perform regular code reviews focusing on data flow from user input to database storage and subsequent display.
Summary
The Custom Field Template plugin for WordPress is vulnerable to Stored Cross-Site Scripting due to improper escaping and sanitization of template configuration values such as labels, titles, and event handlers. Authenticated attackers with contributor-level permissions or higher can inject malicious JavaScript into these fields, which then executes in the browser of any user (including administrators) who accesses the post editor or views the frontend pages where the custom fields are rendered.
Vulnerable Code
// custom-field-template.php line 371 $out .= '<option value="' . $i . '" selected="selected">' . stripcslashes($options['custom_fields'][$i]['title']) . '</option>'; --- // custom-field-template.php line 2123 (and similarly in other event handler loops) $event_output .= " " . $key . '="' . stripcslashes(trim($val)) . '"'; --- // custom-field-template.php line 2146 (rendering JavaScript for the date picker) if ( $dateFormat ) $out_value .= 'Date.format = "' . stripcslashes(trim($dateFormat)) . '"' . ";\n"; --- // custom-field-template.php line 2211 (checkbox labels) if ( $valueLabel ) $out_value .= stripcslashes(trim($valueLabel)); else $out_value .= stripcslashes(trim($value));
Security Fix
@@ -371,9 +371,9 @@ $out .= '<select id="custom_field_template_select">'; for ( $i=0; $i < count($options['custom_fields']); $i++ ) { if ( isset($_REQUEST['post']) && isset($options['posts'][$_REQUEST['post']]) && $i == $options['posts'][$_REQUEST['post']] ) { - $out .= '<option value="' . $i . '" selected="selected">' . stripcslashes($options['custom_fields'][$i]['title']) . '</option>'; + $out .= '<option value="' . $i . '" selected="selected">' . esc_html(stripcslashes($options['custom_fields'][$i]['title'])) . '</option>'; } else - $out .= '<option value="' . $i . '">' . stripcslashes($options['custom_fields'][$i]['title']) . '</option>'; + $out .= '<option value="' . $i . '">' . esc_html(stripcslashes($options['custom_fields'][$i]['title'])) . '</option>'; } $out .= '</select>'; $out .= '<input type="button" class="button" value="' . __('Load', 'custom-field-template') . '" onclick="var post = jQuery(this).parent().parent().parent().parent().attr(\'id\').replace(\'edit-\',\'\'); var cftloading_select = function() {jQuery.ajax({type: \'GET\', url: \'?page=custom-field-template/custom-field-template.php&cft_mode=ajaxload&id=\'+jQuery(\'#custom_field_template_select\').val()+\'&post=\'+post, success: function(html) {jQuery(\'#cft\').html(html);}});};cftloading_select(post);" /> $out_value .= '<script type="text/javascript">' . "\n" . '// <![CDATA[' . "\n"; - if ( is_numeric($dateFirstDayOfWeek) ) $out_value .= 'Date.firstDayOfWeek = ' . stripcslashes(trim($dateFirstDayOfWeek)) . ";\n"; - if ( $dateFormat ) $out_value .= 'Date.format = "' . stripcslashes(trim($dateFormat)) . '"' . ";\n"; + if ( is_numeric($dateFirstDayOfWeek) ) $out_value .= 'Date.firstDayOfWeek = ' . intval($dateFirstDayOfWeek) . ";\n"; + if ( $dateFormat ) $out_value .= 'Date.format = "' . esc_js(stripcslashes(trim($dateFormat))) . '"' . ";\n"; $out_value .= 'jQuery(document).ready(function() { jQuery(".datePicker").css("float", "left"); jQuery(".datePicker").datePicker({'; - if ( $startDate ) $out_value .= "startDate: " . stripcslashes(trim($startDate)); + if ( $startDate ) $out_value .= "startDate: " . esc_js(stripcslashes(trim($startDate))); if ( $startDate && $endDate ) $out_value .= ","; - if ( $endDate ) $out_value .= "endDate: " . stripcslashes(trim($endDate)) . ""; + if ( $endDate ) $out_value .= "endDate: " . esc_js(stripcslashes(trim($endDate))) . ""; $out_value .= '}); });' . "\n" . '// ]]>'. $out_value .= '<label for="' . $id . '" class="selectit"><input id="' . $id . '" name="' . $name . '[' . $sid . '][' . $cftnum . ']' . '" value="' . esc_attr(trim(stripcslashes($val))) . '" ' . $checked . ' type="radio"' . $class . $style . $event_output . ' /> '; if ( isset($valueLabels[$i]) ) - $out_value .= stripcslashes(trim($valueLabels[$i])); + $out_value .= esc_html(stripcslashes(trim($valueLabels[$i]))); else - $out_value .= stripcslashes(trim($val)); + $out_value .= esc_html(stripcslashes(trim($val)));
Exploit Outline
The exploit involves an attacker with Contributor or higher privileges creating or modifying a Custom Field Template configuration. The attacker injects a malicious XSS payload into fields like 'title', 'label', 'valueLabel', or attributes like 'dateFormat' within the template settings. For example, setting a field's title to `<script>alert('XSS')</script>`. When an administrator or another user edits a post that uses this template or views a page where the plugin renders these fields (either in the admin UI meta boxes or on the frontend via the `[cft]` shortcode), the unsanitized values are echoed directly into the HTML or into a script block, causing the payload to execute.
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