“Bugs don’t exist in code. They hide in assumptions.”
A real hacker doesn’t just test a web app. They interrogate it.
Web Application Testing isn’t a process. It’s a form of digital mind-reading — a way to look beyond the surface and see how developers think, where they cut corners, and what they assumed no one would find.
For bug hunters and ethical hackers, Web Application Testing is like exploring a hidden maze, spotting weak spots before they turn into open doors for attackers. It’s not just about running tools or checking off a list—it’s an exciting chase where sharp gut, clever tricks, and a hacker’s brain turn small bugs into big bounty cash. Let’s check out the main ways to test web apps, see how ethical hackers think to catch flaws, and figure out how they link those bugs to score huge rewards.
Table of Contents
The Hacker Mindset: You’re Not Testing Features. You’re Testing Mistakes
When ethical hackers open a login page, they don’t see a form — they see an interface to the backend. When they view source, they don’t see HTML — they see forgotten logic.
Great hackers ask:
What didn’t they think I would do here?
What shouldn’t this input be able to affect?
Where does trust start — and where does it break?
Every web app is a maze, packed with code, logic, and inputs just begging to be poked. Bug hunters don’t just run tests—they dive in, wondering, “What if I tweak this in a way nobody saw coming?” This is where ethical hackers thrive, using their wits to spot flaws and safeguard systems before the bad guys can pounce. It’s a race against time, a battle of wits, and a chance to make a real impact—both in security and in bounty rewards.
The hacker’s mindset is what sets them apart. They don’t just see a login form or a file upload; they see possibilities—ways to twist, break, or bypass. They chain vulnerabilities, turning a small find into a critical exploit, maximizing impact and payouts.
XSS Testing: Planting Seeds of Chaos
Cross-Site Scripting (XSS) is like sneaking a rogue line of code into a website’s chat with its users. It lets hackers slip in malicious JavaScript that can swipe data or take over sessions.
Most people test XSS with . That’s a toy. Hackers test XSS thinking:
Can I steal cookies and bypass HttpOnly?
Can I inject JavaScript that hits their internal API?
Can I make an admin click this from their dashboard?
A bug hunter approaches XSS like a prankster with a megaphone, looking for places to shout their code. They test every input field, URL parameter, and header, asking, “Can I make this page echo my script?” Tools like Burp Suite help, but the magic is in their creativity—trying payloads or obfuscated variants to bypass filters. To chain for high bounties, they escalate a reflected XSS into a stored one, say, by injecting it into a comment that executes for every user, amplifying the impact to session theft or account takeover.
SQL Injection Testing: Open the Database’s Vault
SQL Injection is like slipping a sly command into a web app’s database conversation, letting hackers pull out user data or sneak past login walls.
Can I dump the entire admin table?
Can I perform a time-based blind injection behind a WAF?
Ethical hacker sees every input as a chance to whisper directly to the database. They don’t just type ‘ OR 1=1 — into a login form; they probe systematically, using tools like SQLmap to test parameters and error messages. They ask, “What’s the database hiding?” To chain for big bounties, they might use a blind SQL injection to extract admin credentials, then pivot to an authentication bypass or privilege escalation, turning a data leak into a system takeover.
File Upload Testing: Sneaking Past the Gatekeeper
File upload flaws are like an open window for hackers, letting them sneak in dangerous files—think sneaky scripts or backdoors—that can run wild on the server or mess with users’ devices.
Where is the file stored?
Can I guess the path and execute it?
Can I call it via LFI?
Can I smuggle JS that executes in a PDF viewer or image renderer?
A bug hunter treats file upload fields like unguarded gates. They don’t just upload a PDF; they craft files like an SVG with or a PHP shell disguised as an image. Using tools like Burp Suite, they manipulate extensions, MIME types, or metadata, asking, “Can I trick the server into running my code?”
Directory & Path Discovery: Mapping the Unseen
Directory and path discovery uncovers hidden files, folders, or endpoints, like admin panels or backup files, using tools like Gobuster or Ffuf.
Ethical hacker approaches this like an urban explorer, searching for forgotten alleys in the app’s structure. They ask, “What did the developers leave exposed?” They fuzz URLs with wordlists, looking for /admin/, /backup/, or /.git/. To chain vulnerabilities, they might find a config file with API keys, then use those keys in an SSRF attack to access internal systems, turning a simple find into a critical exploit.
Authentication Bypass Testing: Sneaking Past the Bouncer
Authentication bypass bugs are like finding a side door to a VIP club. Hackers exploit shaky logic or sloppy session handling to stroll into restricted areas without a password.
Ethical hacker sees a login page as a challenge, not a barrier. They test for weak session cookies, predictable tokens, or logic flaws like IDOR (Insecure Direct Object Reference). Using tools like Postman, they ask, “Can I pretend to be someone else?” For big bounties, they chain an authentication bypass with a privilege escalation, accessing admin functions to manipulate critical data or user accounts.
SSRF/LFI/RFI Testing: Sneaking into the System’s Dark Corners
Server-Side Request Forgery (SSRF), Local File Inclusion (LFI), and Remote File Inclusion (RFI) are like secret passages for hackers. These tricks let them mess with server requests or slip in malicious files, often unlocking access to hidden internal systems or juicy data.
Bug hunter views these as keys to the server’s inner sanctum. They test URL parameters or file inputs with payloads like http://localhost or /etc/passwd, using tools like Burp’s Collaborator. They ask, “Can I make the server talk to itself or an external host?” For high bounties, they chain SSRF with a file upload to fetch a malicious script from their server, or use LFI to read sensitive files and pivot to remote code execution.
HTML/JS Analyzers: Decoding the Client-Side Puzzle
Analyzing HTML and JavaScript reveals client-side logic, hidden inputs, or weak validations that can be exploited.
Is there a hidden field?
Is CSRF token static or dynamic?
Does disabled in the HTML actually matter?
Can I submit it from another origin?
Does js file reveal private key?
Ethical hacker treats forms like a codebreaker studying an enemy cipher. They inspect source code with browser dev tools, looking for hidden fields or JavaScript functions that leak tokens or bypass checks. They ask, “What’s the form not telling me?” To chain for bounties, they might combine a client-side XSS with a CSRF vulnerability in a form, automating malicious actions across users to maximize impact.
Chaining for Big Bounties: The Art of Escalation
Bug hunters don’t just report a single XSS or SQL injection—they amplify their findings. For example, a low-severity reflected XSS might seem minor, but chaining it with a CSRF to steal admin sessions makes it critical. Or, finding a file upload vulnerability is great, but using it to upload a shell and then triggering it via SSRF to hit an internal server? That’s a payout multiplier. Hackers think like architects, building a chain of exploits that shows maximum damage—ethically, of course—to prove the risk and earn those high rewards.
Your job as a bug hunter isn’t just to find bugs. It’s to:
Understand how everything connects.
Think like a developer — and then like an attacker.
Chain the unchainable.
Prove impact beyond question.
