Interacting with a backend database to retrieve and write data is one of the most critical tasks performed by a web application. Relational databases that store the data in a series of tables are the most common way to accomplish this, and for querying information, Structured Query Language (SQL) is the de facto standard.
In order to allow users to select what information to see or to filter what they can see according to their profiles, the input taken from cookies, input forms, and URL variables is used to build SQL statements that are passed back to the database for processing. As user input is involved in building the SQL statement, the developer of the application needs to validate it carefully before passing it to the backend database. If this validation is not properly done, a malicious user may be able to send SQL queries and commands that will be executed...