A tester evaluates a login form that builds SQL queries using unsanitized input.

The CEH Web Application Attacks module explains tautology-based SQL injection as an attack where input alters a conditional statement to always evaluate as TRUE (e.g., ' OR ' 1 ' = ' 1 ' ).

Submitting a single quote often breaks query logic and allows attackers to manipulate authentication conditions.

Option D is correct.

Option A extracts data.

Option B relies on error messages.

Option C uses timing delays.

CEH identifies tautology attacks as one of the earliest and most common SQL injection techniques.