If the page returns an error (like "The used SELECT statements have a different number of columns"), the attacker will try again with five or seven NULL values until the error disappears. 4. -- (The Comment) In SQL, double-dashes signify the start of a comment.
If the page loads normally, the attacker knows the database is expecting 6 columns. If the page returns an error (like "The
Scanners append strings like GoJB so that the security researcher can search the website's logs or the page's source code later to confirm that their input was successfully processed and reflected by the server. Summary of the Attack Flow If the page loads normally, the attacker knows
This string is a classic example of a used by security researchers and attackers to probe a website's database for vulnerabilities. : Any code that was supposed to follow
: Any code that was supposed to follow the input (like a closing quote or a WHERE clause) is ignored by the database, preventing syntax errors that would break the injection. 5. GoJB
: For a UNION to work, the second query must have the exact same number of columns as the first query. 3. SELECT NULL,NULL,NULL,NULL,NULL,NULL
: NULL is used because it is compatible with almost any data type (integers, strings, dates, etc.).