Attack Chain

1. Initial Access with Low-Privilege API Key: An attacker obtains a valid, low-privileged API key, for example, a token with allowget=1 on the clientes resource and fullaccess=0, typically intended for integrations or limited data retrieval.
2. Crafted SQL Injection Request: The attacker sends a GET request to a vulnerable API endpoint, such as /api/3/clientes, including a maliciously crafted filter parameter. The payload within the filter parameter contains SQL injection syntax, specifically leveraging parentheses to bypass the Where::sqlColumn() escaping mechanism (e.g., filter[(0)UNION SELECT ...]=).
3. Database Query Manipulation: The FacturaScripts backend processes the request, and due to the Where::sqlColumn() bypass, the attacker's SQL payload is concatenated directly into the database query, allowing for arbitrary SQL execution.
4. Information Leakage (Password Hash): The injected SQL query (e.g., UNION SELECT IFNULL(password,2),... FROM users WHERE(nick='admin')) extracts sensitive data like the admin user's bcrypt password hash from the users table.
5. Information Leakage (Session Cookie): The attacker repeats the process with a modified SQL injection payload to extract the admin user's logkey (web session cookie value).
6. Session Hijacking: With the leaked logkey, the attacker creates a forged session cookie for the admin user.
7. Account Takeover: The attacker uses the forged session cookie to access administrative interfaces (e.g., /AdminPlugins) of the FacturaScripts application, achieving full administrative account takeover.
8. Arbitrary Command Execution (Optional): Time-based blind SQL injection techniques (e.g., (SELECT(SLEEP(2)))) can also be employed to confirm the vulnerability in scenarios where UNION SELECT isn't feasible due to column count mismatches.

Impact

The successful exploitation of this vulnerability leads to a severe cross-resource confidentiality breach and complete account takeover. An attacker starting with only a read-only API key for a single resource can escalate privileges to full administrator access. This allows them to read any data from any database table, including user credentials (password hashes), API keys, and sensitive business information. The attacker gains the ability to hijack administrator web sessions, granting them unfettered control over the FacturaScripts instance, including the installation of plugins, modification of settings, and potential data exfiltration or manipulation. The attack bypasses existing serialization protections for sensitive fields and API key scoping, making it a critical threat to data security and system integrity.

Recommendation

• Deploy the Sigma rule Detect FacturaScripts Authenticated SQL Injection Attempt to your webserver logs to identify attempts at this exploitation.
• Review webserver access logs for requests containing patterns like filter%5B%28 combined with UNION%20SELECT or SLEEP%28 in cs-uri-query.
• Patch FacturaScripts installations immediately to address GHSA-5qmh-x653-g8qj once a fix is available, prioritizing internet-facing instances.
• Implement stringent API key management, including regular rotation and least-privilege principles, though this vulnerability demonstrates how such controls can be bypassed.
• Monitor for unusual administrator logins or activities originating from new or unexpected IP addresses, especially after suspicious API requests.