📰 Originally published on SecurityElites — the canonical, fully-updated version of this article.
🧪 DVWA LAB SERIES
FREE
Part of the DVWA Complete Lab Series
Lab 27 of 30 · 90% complete
⚠️ Lab Environment Only: All techniques in DVWA Source Code Review Lab use DVWA running on your own local machine. Never apply these techniques against systems you do not own or have explicit written authorisation to test. SecurityElites.com accepts no liability for misuse.
Most people who use DVWA never click the View Source button. They set the security level to Low, fire payloads until something works, screenshot the output, and move on. I understand why — the exploitation is the exciting part. But that habit builds a practitioner who needs trial and error on every engagement rather than one who reads the code, understands the vulnerability, and constructs the right payload on the first attempt.
On a white-box web application assessment last year, the client gave me access to the PHP source code alongside the running application. The codebase had 40,000 lines. I found three critical SQL injection points in eleven minutes — not by running SQLMap, but by searching the source for the pattern $_GET and $_POST variables being concatenated into query strings. The source told me exactly which parameters to target, what the query structure was, and what payload would extract the data. DVWA’s View Source button teaches exactly that skill — reading what the application actually does with your input before you decide what to send it. Lets start with our DVWA Source Code Review Lab.
🎯 What You’ll Master in Lab 27
Use DVWA’s View Source to read PHP backend code across all security levels
Identify the vulnerable code pattern for SQL injection, XSS, command injection, and file inclusion
Compare Low, Medium, High, and Impossible source — understand what each level adds
Map source code findings directly to targeted exploit payloads
Identify bypassable blacklists in Medium security and construct bypass payloads from the source
Write source-informed remediation recommendations for a professional report
⏱️ Lab 27 · 3 exercises · DVWA running locally ### ✅ Prerequisites - DVWA running locally — DVWA Lab Setup Guide if you need it - DVWA SQL Injection Lab — you need to have exploited SQLi first; today you will read the source that makes it vulnerable - DVWA XSS Reflected Lab — same: exploit first, then Lab 27 shows you the source behind it - Basic PHP reading ability — you do not need to write PHP, just recognise patterns in existing code ### 📋 DVWA Source Code Review Lab 27 — Contents 1. The View Source Button — How DVWA Exposes Its Own Code 2. SQL Injection Source Review — Low to Impossible 3. XSS Source Review — Where Output Goes Unescaped 4. Command Injection Source Review — Shell Passthrough Patterns 5. File Inclusion Source Review — Path Traversal in PHP 6. Writing Source-Informed Remediation Recommendations #### How often do you use DVWA’s View Source button? Never — I test black-box only Only after I’ve found the exploit Before exploiting — to understand the code I compare all security levels every time
Labs 1 through 26 taught you to exploit every major vulnerability class in DVWA. Lab 27 turns that around — instead of probing from outside, you read the code that makes each one exploitable. The DVWA lab series covers 30 labs total. Lab 28 is the final pentest report exercise where you document everything. Understanding the source code behind each vulnerability is what makes your Lab 28 report findings technically precise rather than generic.
The View Source Button — How DVWA Exposes Its Own Code
Every DVWA module has two buttons at the bottom of the page: View Source and View Help. View Source is the one that changes how you think about web application security testing. It shows you the exact PHP code processing your input for the current security level. More importantly, Compare All Levels shows Low, Medium, High, and Impossible in the same window — four versions of the same feature, each representing a different developer’s approach to the same security problem.
The way I use these buttons on every DVWA module: first I exploit the Low level by trial and error to build intuition. Then I open View Source and read exactly why the payload worked. Then I look at Medium and High to understand what the developer changed — and whether those changes are sufficient. The Impossible level is what I read when writing the remediation section of a report: it shows the correct fix rather than leaving me to write “use parameterised queries” without showing the client what that looks like in their specific code.
DVWA SOURCE CODE — KEY PHP PATTERNS TO RECOGNISECopy
── VULNERABLE PATTERNS ───────────────────────────────────────
SQL Injection — raw variable in query string
$query = “SELECT * FROM users WHERE user_id = ‘$id’;”;
Variable $id comes from $_GET[‘id’] with no sanitisation
Command Injection — variable passed to shell_exec
$cmd = shell_exec(‘ping -c 4 ‘ . $target);
$target from $_POST[‘ip’] — attacker appends ; whoami
XSS Reflected — raw echo of user input
echo ‘
Hello ‘ . $_GET[‘name’] . ‘’;
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