{keyword}') Union All Select Null,null,null,null,null,null,null,null-- - Mxyc

: This is the SQL comment symbol. It tells the database to ignore everything else in the original code, effectively "turning off" the security checks or logic that were supposed to happen next. The Goal: Data Exfiltration

Here is a look into what that string is designed to do and why it’s a fundamental concept in web security. What is this string?

It looks like you've included a in your request. In the world of cybersecurity, that specific snippet is a classic example of an "Union-based" attack. : This is the SQL comment symbol

: This is the heart of the attack. It tells the database to combine the results of the original (legitimate) search with a new set of data the attacker wants to see.

: Attackers use NULL to figure out exactly how many columns the original database table has. If the number of NULL s matches the columns, the page loads; if not, it crashes. What is this string

The text ') UNION ALL SELECT NULL,NULL...-- is a malicious payload used to test for vulnerabilities in a database.

Modern web development has largely moved past this threat using a technique called (or Parameterized Queries). Instead of letting user input mix directly with the code, the database is told: "Treat this input strictly as text, no matter what symbols are inside it." : This is the heart of the attack

: This attempts to "break out" of the developer’s intended code by closing a data field and a function.