How to Start Bug Hunting: A Practical Guide

If you already understand vulnerabilities like XSS, SQL Injection, IDOR, SSRF, and Command Injection, have completed a lot of PortSwigger labs, and feel comfortable with web security concepts, the next question is usually:
How do I actually start bug hunting? 🎯
The biggest change at this stage is learning how to think like a hunter. Instead of only solving a lab with a known vulnerability, you need to learn how to explore a target, understand its attack surface, identify interesting functionality, and decide what to test first.

Start by Watching Real Bug Hunters​

One of the best ways to understand real-world bug hunting is to watch experienced hunters work through targets.
Don't focus only on the tools they use. Pay attention to how they think.

Look at questions such as:

• How do they start reconnaissance?
• How do they discover subdomains?
• How do they find URLs and endpoints?
• How do they map the attack surface?
• Which functionality do they investigate first?
• Why do they decide to test one feature instead of another?
• What makes them suspicious about a particular parameter or request?

This is important because real bug hunting is rarely just about knowing a long list of vulnerabilities.
You need to learn how to turn a large application into smaller areas that you can understand and test systematically. 🔎

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Reconnaissance Is a Core Part of Bug Hunting​

Recon is one of the most important parts of the process because you cannot properly test an attack surface that you don't know exists.
Imagine an authorized target with 20 discovered subdomains.
If each subdomain exposes around 50 interesting URLs, you could potentially have around 1,000 URLs and endpoints to understand and test.
That doesn't mean you will find a vulnerability. More endpoints do not automatically mean more bugs.
However, understanding the target's attack surface gives you more opportunities to identify unusual behavior, weak access controls, unexpected input handling, and other security issues.
The goal is not simply to collect as many URLs as possible.
The goal is to understand what the application does and where its interesting functionality is located.

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Build Your Own Bug Hunting Methodology​

After watching several experienced hunters, you will notice that they don't all follow exactly the same process.
One hunter may focus heavily on recon.
Another may spend more time understanding application functionality.
Someone else may specialize in access control issues, authentication, APIs, or client-side behavior.
That's useful because there is no single workflow that you have to copy exactly.
Instead, observe different approaches and gradually build a methodology that makes sense to you.

A simple methodology might look like:

1. Identify the authorized target and its scope.
2. Map the application's attack surface.
3. Discover interesting functionality and endpoints.
4. Understand how requests and data flow through the application.
5. Identify areas that may be security-sensitive.
6. Choose a specific vulnerability class to investigate.
7. Test your hypothesis carefully.
8. Document what you found and how you reached it.
9. Reproduce the issue safely when appropriate.

With experience, this process becomes more natural.

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Don't Try to Learn Every Vulnerability at Once​

A common mistake is trying to hunt for everything simultaneously.
You might know XSS, IDOR, SSRF, SQL Injection, CSRF, authentication issues, and many other vulnerability classes, but trying to test all of them at the same time can make your process unfocused.
Instead, pick one vulnerability class and concentrate on it.
For example, start with XSS.
Study XSS carefully on PortSwigger, complete the relevant labs, and try to develop your own process for recognizing and testing XSS in an authorized real-world target.
Then spend some time hunting specifically for XSS.
You don't need to find a bug every day.
The goal is to understand the vulnerability well enough that, when you encounter an interesting input or feature, you can recognize when it deserves investigation.

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Turn Every Bug Into a Learning Process​

Finding a vulnerability is not the end of the learning process.
When you find a bug, stop and ask yourself:

• Why did I suspect this functionality?
• What made the behavior unusual?
• How did I discover the vulnerable endpoint?
• Which requests did I investigate?
• What was the first useful clue?
• Could I recognize a similar situation on another target?
• What part of my process could be improved?

This is where a single vulnerability can become much more valuable.
Instead of remembering only what the bug was, you start understanding how you discovered it.
That discovery process is what you can reuse.

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Keep Practicing Older Vulnerabilities​

When you move from one vulnerability to another, don't completely abandon what you already learned.
For example, you might start with XSS and later begin studying IDOR.
While learning IDOR, continue looking for XSS during your authorized testing.
You can gradually combine the two approaches.
Over time, add more vulnerability classes to your methodology without losing the ability to recognize the ones you already understand.
The goal is to reach a point where you can look at an application and naturally think:
"This feature looks interesting. What could go wrong here?" 🧠

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Use PortSwigger to Build Strong Fundamentals​

PortSwigger Web Security Academy is particularly useful for building a strong foundation because you can study a vulnerability and then immediately practice it in controlled labs.

A useful learning cycle is:

1. Study the vulnerability.
2. Understand why it happens.
3. Learn how it can be identified.
4. Solve related labs.
5. Practice recognizing the same patterns in authorized applications.
6. Document what you learned.
7. Move to another vulnerability while continuing to review the previous ones.

Don't rush through the labs just to increase the number of completed exercises.
Understanding why the solution works is much more valuable than simply remembering the steps.

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Continue With Practical Training​

After building a solid web security foundation with PortSwigger, you can also use platforms such as TryHackMe to strengthen your fundamentals and practical skills.
Later, when you feel ready for more challenging environments, Hack The Box can provide additional hands-on practice.
The important thing is to treat these platforms as part of your overall learning process rather than as a race.
Your goal is to improve your ability to understand systems, recognize security problems, and investigate them methodically.

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Don't Measure Progress Only by the Number of Bugs​

One of the easiest ways to get frustrated with bug hunting is expecting yourself to find vulnerabilities constantly.
That is not a useful measurement of progress, especially when you're starting.
Some days you may spend hours investigating an application and find nothing.
You may discover that an interesting-looking behavior is completely secure.
You may spend time understanding an API without finding a reportable issue.
Those experiences still teach you something.

Over time, you are building:

• Better reconnaissance skills
• Better attack-surface awareness
• Better understanding of application behavior
• Better vulnerability recognition
• Better testing methodology
• Better debugging and investigation skills
• Better judgment about where to spend your time

That's a much more sustainable way to improve.

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A Simple Bug Hunting Roadmap​

You can think about the learning process like this:
Phase 1 - Build the Fundamentals
Learn common web vulnerabilities and understand how they work.
Phase 2 - Practice in Labs
Use PortSwigger Web Security Academy to practice individual vulnerability classes.
Phase 3 - Learn From Real Hunters
Watch experienced researchers and focus on their methodology, not just their tools.
Phase 4 - Build Your Recon Process
Learn how to understand the authorized target's subdomains, URLs, endpoints, APIs, and functionality.
Phase 5 - Focus on One Vulnerability
Pick one vulnerability class and hunt specifically for it.
Phase 6 - Expand Gradually
Add new vulnerability classes while continuing to practice the old ones.
Phase 7 - Build Your Own Methodology
Combine everything into a workflow that you understand and can repeat.

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The Real Goal of Bug Hunting​

When you first start bug hunting, it's easy to think the goal is simply to find vulnerabilities.
But there is another skill being developed at the same time:
your ability to think like a security researcher. 🧠
You are learning how to look at an application, understand its behavior, form a hypothesis, test that hypothesis, and learn from the result.
Don't worry about becoming an expert overnight.
Focus on one vulnerability, understand it deeply, practice it repeatedly, and gradually expand your methodology.
The bugs will come with experience. The more important thing you're building in the beginning is the way you think about security problems.

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Frequently Asked Questions​

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How should I start bug hunting as a beginner?​

Start by building strong web security fundamentals, practice vulnerabilities through PortSwigger labs, study how experienced hunters approach targets, and gradually develop your own methodology. Always practice on authorized targets.

Should I learn every vulnerability before starting bug hunting?​

No. You can start with one vulnerability class, understand it deeply, and gradually add others as your experience grows.

Is recon important for bug hunting?​

Yes. Understanding the authorized target's attack surface helps you identify interesting functionality, endpoints, and areas that deserve further investigation.

Do I need to find a bug every day?​

No. Finding vulnerabilities is not a reliable daily measure of progress. Learning how to investigate applications and improving your methodology are also important parts of becoming a better hunter.

What should I do after finding a vulnerability?​

Study how you found it. Understand what made you suspicious, how you reached the vulnerable functionality, and whether you can recognize the same pattern elsewhere in an authorized environment.