What practice can make an application or database server vulnerable to SQL injection attacks?

Allowing entries that contain binary data, escape sequences, and comment characters can significantly increase the risk of SQL injection attacks. SQL injection vulnerabilities arise when an application improperly processes user input that is directly concatenated into SQL queries without sufficient validation or sanitization.

When an application permits characters commonly used in SQL statements, such as single quotes, semicolons, or other special characters, malicious users may exploit this permission by injecting their own SQL commands into the application's queries. This can lead to unauthorized data access, modification, or even deletion of stored data.

In contrast, using prepared statements, sanitizing user input, and limiting database permissions are best practices that help mitigate the risks associated with SQL injection. Prepared statements parameterize SQL queries, thus preventing user input from being treated as code. Sanitizing user input involves validating and escaping potentially harmful characters before processing the input. Limiting database permissions restricts what actions a compromised account can perform, thereby minimizing potential damage from an SQL injection attack.