The vulnerability described allows an attacker to manipulate the query string in the URL to alter the SQL query executed by the server. This is a classic example of a SQL Injection attack, where the attacker inserts or “injects” malicious SQL code into the query, which can lead to unauthorized access to database information. The altered URL http://www.ec-sell.com/products.jsp?val=200 OR '1'='1 is a typical SQL injection payload that forces the SQL query to return all products by making the WHERE clause always true ('1'='1).

To protect against SQL Injection attacks, developers should:

Use Prepared Statements: These include parameterized queries that separate SQL logic from data, preventing attackers from modifying the SQL query.

Employ Stored Procedures: They encapsulate the SQL logic on the server side and prevent exposure to SQL injection.

Validate User Input: Ensure that all user-supplied data is validated for type, length, format, and range.

Implement Error Handling: Avoid revealing detailed error messages that could give attackers clues about the database structure.

References: The EC-Council’s Certified Application Security Engineer (CASE) Java documentation outlines the importance of secure coding practices to prevent common vulnerabilities like SQL Injection12. Additionally, the training materials cover various defensive programming techniques that are essential for creating secure Java applications, including those that prevent SQL Injection attacks345.