Blind SQL injection with time delays

Platform: PortSwigger | Category: SQL_injection | Type: Lab | Difficulty: N/A | OS: N/A | Author: XESXOR | Date: 2026-08-24 | Status: Solved Techniques: Web Security Academy, SQL_injection

Summary

Walkthrough of the PortSwigger Web Security Academy lab Blind SQL injection with time delays (SQL_injection). This lab demonstrates a sql_injection vulnerability and its exploitation to achieve the lab objectives.

Lab Overview

PortSwigger Web Security Academy — SQL_injection

This writeup is part of the XESXOR PortSwigger collection. The original lab description and solution have been preserved and reformatted for clarity.

Lab Description :

Overview :

it is often possible to exploit the blind SQL injection vulnerability by triggering time delays conditionally, depending on an injected condition. Because SQL queries are generally processed synchronously by the application, delaying the execution of a SQL query will also delay the HTTP response. This allows us to infer the truth of the injected condition based on the time taken before the HTTP response is received.

The techniques for triggering a time delay are highly specific to the type of database being used. On Microsoft SQL Server, input like the following can be used to test a condition and trigger a delay depending on whether the expression is true:

 sql read-only • copy allowed Copy
'; IF (1=2) WAITFOR DELAY '0:0:10'--
'; IF (1=1) WAITFOR DELAY '0:0:10'--

The first of these inputs will not trigger a delay, because the condition 1=2 is false. The second input will trigger a delay of 10 seconds, because the condition 1=1 is true.

Using this technique, we can retrieve data in the way already described, by systematically testing one character at a time:

 sql read-only • copy allowed Copy
'; IF (SELECT COUNT(Username) FROM Users WHERE Username = 'Administrator' AND SUBSTRING(Password, 1, 1) > 'm') = 1 WAITFOR DELAY '0:0:{delay}'--

Solution :

Cause a 10 sec delay in response -

The request looks like this

SLEEP command differs for each type of databse, here we find it by trial & error method that it is a POSTgreSQL database

To do this we can use the following payload

 sql read-only • copy allowed Copy
TrackingId=x'||pg_sleep(10)--

We get a response after 10 sec which confirms the SQL injection vulnerability.

Key Takeaways / Lessons

• Understanding SQL_injection detection and exploitation is crucial for web security.
• Always validate and sanitize user input; implement proper access controls.
• This lab is part of the PortSwigger Web Security Academy — practice in a safe, legal environment.

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Crafted by XESXOR Research • 2026-08-24 • PortSwigger Web Security Academy • Lab: Blind SQL injection with time delays