Detailed Technical Analysis of the Write-up on MyBB SQL Injection via Unauthenticated User

Overview:
The write-up by Stefanocoding details a SQL Injection vulnerability in MyBB, a popular open-source forum software. Specifically, the discussed vulnerability affects a MyBB plugin called "Thank You/Like," enabling an unauthenticated user to exploit the flaw, potentially leading to severe data breaches and full system compromise.

Key Technical Details:

1. Vulnerability Description:
   The vulnerability is a Boolean-based Blind SQL Injection in the MyBB plugin "Thank You/Like" (thankyoulike.php). Boolean-based Blind SQL Injection relies on sending SQL queries to the database in such a way that the application's response reflects whether the query is true or false. This method can be used to systematically retrieve data one bit at a time.

2. Examining the Exploit Path:

3. Unauthenticated Access: The exploit works without authentication, leveraging a flaw in how the plugin constructs SQL queries.

4. Vulnerable Endpoint: The vulnerability is located in the thankyoulike.php file, specifically in the AJAX request handling section. This part processes user input directly in SQL statements without proper sanitization.

5. Exploit Scenario:
   To perform the attack, the attacker sends a HTTP GET request to the vulnerable endpoint with a crafted parameter designed to manipulate the SQL query.

plaintext GET /inc/plugins/thankyoulike.php?tid=2%20AND%201=1 HTTP/1.1 Host: target.com ... - Logical Evaluation: If 1=1 (always true), it indicates the successful injection. - An alternative injection, such as AND 1=2 (always false), helps confirm the vulnerability by contrasting responses.

1. Proof of Concept (PoC):
   By tailoring the GET request, the attacker confirms the blind SQL injection vector.

plaintext GET /inc/plugins/thankyoulike.php?action=post&pid=XXXXXX' AND (SELECT user FROM mysql.user LIMIT 0,1)='root' -- - In the above payload: - pid=XXXXXX' injects the payload. - AND (SELECT user FROM mysql.user LIMIT 0,1)='root' attempts to compare the fetched user from the database with 'root'.

• If the user exists and matches root, the response differs, alerting the attacker of valid injection.

• Response Behavior:
  Boolean-based blind SQL injection does not provide direct feedback (e.g., database errors). Instead, the attacker must infer the presence of the vulnerability from subtle changes in the application's responses due to the injected SQL.

• Further Exploitation:
  With the injection vector confirmed, an attacker can retrieve data by systematically injecting payloads to test each character's presence in target values (exfiltration).

• Mitigation Strategies:

• Prepared Statements: Use prepared statements with bound parameters to prevent SQL injection.
• Input Validation: Validate and sanitize all user inputs before they interact with the database. Specifically, input filtering should be employed to eliminate any potentially dangerous SQL meta-characters.
• Access Control: Limit access to plugin endpoints and ensure that sensitive routines are not exposed to unauthenticated users.
• Security Patches: Apply patches and security fixes released by MyBB and plugin developers immediately.

Key Takeaways:

• Danger in Plugins: Third-party plugins introduce significant risk, especially when they handle database operations without proper sanitization or validation.
• Blind SQL Injection: Boolean-based blind SQLi, while harder to detect, is remarkably powerful for unauthorized data retrieval.
• Security Best Practices: Implement strong input validation and prefer prepared statements to mitigate SQLi risks effectively.
• Access Controls: Ensure that critical functions, especially those modifying or accessing sensitive data, are authenticated and authorized adequately to limit exposure to potential vulnerabilities.

Conclusion:

The identified SQL injection vulnerability in MyBB's "Thank You/Like" plugin exemplifies the dangers posed by improper handling of user inputs in third-party plugins. Ensuring proper sanitization, input validation, and using secure coding practices are vital to maintaining the integrity and security of web applications and associated plugins. This analysis underscores the importance of regular security reviews and timely updates within open-source components and plugins.

For full details and further technical breakdown, refer to the original gist.