Companies often unintentionally expose files or documents on their public-facing servers, websites, or third-party services like GitHub or AWS S3 buckets. These files could include configuration files, source code, PDFs, text files, or other documents that might contain sensitive information that can help identify vulnerabilities. By analyzing these files carefully, you can uncover several types of security issues that could potentially lead to exploitation. Let’s break down each of these points in more detail:
1. Sensitive Data Exposure
Sometimes, files exposed online contain sensitive data like API keys, credentials, or personally identifiable information (PII). These are critical pieces of information that could allow attackers to compromise an application, service, or even gain unauthorized access to sensitive accounts. For example, API keys left exposed can give an attacker access to a system’s back-end or third-party services. Exposed PII can lead to identity theft or privacy violations. It’s essential to scan through exposed files for these sensitive items to ensure they’re not inadvertently shared.
2. Misconfigurations
A common issue is misconfigured servers or services. This happens when systems are not properly set up, leaving them vulnerable to attack. Misconfigurations can involve incorrect permissions on storage services, publicly accessible database configurations, or open ports that shouldn’t be exposed. These flaws can be discovered by carefully analyzing the exposed files for any signs that the environment hasn’t been hardened. In many cases, a simple misconfiguration can give attackers the ability to escalate privileges or gain access to more sensitive parts of the system.
3. Hidden Endpoints
Exposed files can sometimes reveal undocumented APIs or internal URLs that were not meant to be publicly accessible. These “hidden” endpoints can provide attackers with a backdoor into the system, bypassing normal security checks or access controls. Finding these endpoints through careful inspection of source code or configuration files can provide a way to exploit the system and gain unauthorized access to sensitive data or services. It’s important to be vigilant and spot these hidden endpoints, as they are often overlooked by developers.
4. Business Logic Flaws
In some cases, exposed documents or files can reveal flaws in the business logic of an application. These flaws can give you insights into how the application works, which can be used to manipulate the system or perform unauthorized actions. For example, a vulnerable payment system might accept requests with invalid data due to a weak business logic implementation. By carefully analyzing the files, you can identify patterns and weaknesses in the system’s design that could be leveraged for exploitation.
5. Outdated Software
Sometimes, exposed files contain references to outdated libraries or systems with known vulnerabilities. For example, an old version of a framework or library might be included in a configuration file or a piece of documentation. These outdated components can be exploited if attackers are aware of their vulnerabilities. Identifying these outdated systems or libraries early allows companies to patch them before they’re exploited in the wild.
Why Manual Testing Matters:
While automated tools are incredibly useful for quickly scanning large amounts of data, manual testing plays a crucial role in finding these types of issues. Automated tools often focus on surface-level scans, but manual testing allows you to dig deeper, analyze context, and think like an attacker. By reading through the exposed files and understanding the underlying logic, you can identify subtle security weaknesses that automated tools might miss. Manual testing also allows you to adapt to complex scenarios and better understand how different components of a system interact, which is key for finding vulnerabilities.
By carefully analyzing exposed files and using manual testing techniques, you can uncover critical security flaws that could otherwise go unnoticed, helping companies improve their security posture and, in some cases, even earning rewards for your efforts.
This approach works really well because it takes advantage of information that’s already publicly available. As long as you stick to what’s allowed and don’t go beyond the boundaries, this kind of testing is typically within the scope of bug bounty programs.
Steps for Investigating Exposed Files in Bug Bounty Programs
1. Find Exposed Files and Documents
The first step is to locate files or documents that a company may have unintentionally made public, either on their website or through third-party platforms. Here’s how you can go about it:
A. Google Dorking:
Use advanced search queries to pinpoint specific file types or paths. Some useful examples include:
site:*.target.com filetype:pdfsite:target.com inurl:(config | backup | admin)site:target.com -inurl:(login | signup)(to exclude common login or signup pages)
B. Wayback Machine:
Check the Internet Archive at archive.org to see past versions of the site. You might find files that have since been removed or were left exposed in the past.
C. Subdomain Enumeration:
Use tools like Subfinder or Amass to discover subdomains related to the target company. You may find subdomains hosting files, for example, files.target.com.
D. Directory Brute-Forcing:
Tools like dirb, gobuster, or ffuf can help you find directories with exposed files on a website. Common ones include /config, /backup, and /docs.
9. GitHub Recon:
Search for public repositories related to the company using keywords like target.com. This can sometimes reveal source code or files accidentally uploaded by developers.
10. X Posts and Forums:
Search through X (formerly Twitter) or hacker forums for mentions of the company. Other researchers or hackers might have already shared valuable findings, but always verify the information independently.
2. Know Which File Types to Focus On
Once you’ve found exposed files, the next step is figuring out which ones are worth your time. Some file types are more likely to contain useful or sensitive information. Here’s what to keep an eye out for:
A. Configuration Files (.env, .conf, .ini, .xml, .json):
These often hold important details like database credentials, API keys, tokens, or service configs. A leaked .env file can sometimes give you full access to internal systems.
B. Source Code Files (.js, .php, .py, .html):
These can reveal hidden endpoints, hardcoded secrets, or logic flaws. JavaScript files, in particular, might contain API calls or references to backend routes that aren’t visible from the main site.
C. Documents (.pdf, .docx, .txt):
Don’t skip over docs—things like internal manuals, employee onboarding guides, or architecture diagrams might contain useful intel or hint at deeper flaws.
D. Log Files (.log):
Logs often contain stack traces, server errors, or even sensitive request data. They can be especially helpful when hunting for misconfigurations or backend leaks.
E. Backup Files (.bak, .zip, .tar.gz):
These are like treasure chests—old versions of websites, databases, or configs can expose information that shouldn't be online anymore but still is.
3. Analyze the Content Carefully
After you’ve gathered files, the real work begins — going through them with a sharp eye. You’re not just looking for code or text — you’re looking for clues that might lead to vulnerabilities. Here’s what you should be paying attention to, and why each of them matters:
Credentials and Secrets
A. What to look for: Things like api_key, password, secret, token, aws_access_key, private_key, or similar keywords.
B. Why it matters: If these are exposed, they can open doors to sensitive areas like databases, cloud services, or internal APIs — without needing to hack anything.
C. Real-world example: Finding something like DB_PASSWORD=supersecret123 in a .env file could be all you need for a valid bug report.
Endpoints and URLs
A. What to look for: Strings like http://, https://, /api/, endpoint=, or url= inside source code or docs.
B. Why it matters: These URLs can point to hidden or internal APIs that might not be properly secured. Some could be vulnerable to SQL injection, XSS, or IDOR (Insecure Direct Object Reference).
C. Real-world example: A JavaScript file that exposes something like /api/v1/userdata?id=123 is a great candidate for IDOR testing.
Error Messages and Stack Traces
A. What to look for: Keywords like exception, error, traceback, SQL queries, file paths, or debug logs.
B. Why it matters: These give away what’s happening behind the scenes — like what technologies are in use, where queries happen, or how things break when something goes wrong.
C. Real-world example: A log that says SELECT * FROM users WHERE id = '1' could suggest the system is vulnerable to SQL injection.
Version Information
A. What to look for: References to specific versions of tools or libraries, like Apache 2.4.29, jQuery 1.8.3, etc.
B. Why it matters: Older software often has known vulnerabilities (CVEs). If you can match the version to a known issue, that’s a solid lead.
C. Real-world example: If a PDF mentions “Powered by OpenSSL 1.0.1”, and that version has known exploits, you’ve got something valuable.
Sensitive Data
A. What to look for: Personally identifiable info (PII) like full names, email addresses, Social Security Numbers (SSNs), phone numbers, financial details, or even internal IPs.
B. Why it matters: Leaking sensitive user or company data is a big deal — and often leads to valid bounty submissions.
C. Real-world example: A misconfigured S3 bucket containing a .csv file with customer data like emails or phone numbers is a strong finding.
Business Logic Clues
A. What to look for: Anything that hints at how the application works — like descriptions of roles, permissions, workflows, or approval steps.
B. Why it matters: Understanding the logic helps you spot things like privilege escalation, bypasses, or misuses that automated scanners would miss.
C. Real-world example: If a document says, “Admins can approve users via /admin/approve”, that endpoint might be unprotected or accessible to normal users.
Going through a bunch of files manually can get tiring — and that’s where a few handy tools come in. These can speed up your workflow and help you focus on spotting the actual vulnerabilities rather than getting lost in a sea of text.
Quick Text Searching
A. Use this when you have a folder full of files and want to quickly spot keywords like password, api_key, or token.
B. Commands:
grep -r "api_key" /path/to/files
grep -r "password" *.jsC. Windows? You can use findstr the same way. It's super helpful when scanning logs, configs, or source files.
Code Review Editors
A. Use editors like VS Code, Sublime Text, or Notepad++ — they make searching and reading large files a lot easier.
B. Use regex search inside these editors to find things like credentials, tokens, or URLs faster.
Deobfuscate JavaScript
A. Sometimes, JavaScript files look like gibberish — that’s obfuscation.
B. Tools like jsbeautifier.org or built-in browser beautifiers can help clean up the code and make it readable.
Extracting Text from PDFs or Docs
A. Need to analyze a PDF or Word document? Use tools like:
pdftotext(for PDFs)catdoc(for Word.docfiles)
B. These let you convert them to plain text so you can easily search or review them.
Automation Tools for Secrets
A. Tools like truffleHog and GitLeaks are built to scan code and files for exposed secrets automatically.
B. Super useful if you’re digging through GitHub repos or large codebases.
Finding something interesting is great — but before jumping to report it, make sure it actually matters. Raw data isn’t always useful unless you’ve checked how it behaves in the real world.
Test Within Scope
A. Found an API key? Don’t just assume it’s valid. Try using it (safely and ethically) to see if it gives access to something — maybe a dev panel, an S3 bucket, or an API response.
B. Got a new endpoint? Test it for common issues like:
- XSS — Try injecting a simple
<script>tag. - SQL Injection — Throw in a
' OR 1=1--and watch the response. - IDOR — Change an ID in the URL and see if you can access another user’s data.
Watch Out for Traps
A. Some exposed data might be intentional — like honeypots or fake keys left to catch bad actors.
B. If something feels too easy or “bait-like,” double-check if it’s part of a bug bounty challenge or demo site.
Use the Right Tools
A. Burp Suite: Perfect for analyzing requests and responses, modifying inputs, and seeing how the backend reacts.
B. Postman: Great for working with APIs — send requests, add headers, and test endpoints without much setup.
Once you’ve confirmed your finding is valid and within scope, it’s time to document everything. A good report isn’t just about what you found — it’s about how you explain it.
Break Down Your Report Like This:
A. Title: Keep it straight to the point.
Example: Publicly Exposed API Key in Config File
B. Description: Tell the story.
What did you find, and why does it matter? Keep it clear and to the point so even a non-technical reviewer can follow.
C. Steps to Reproduce:
Show exactly how you found it. List the dork you used, tools involved, the file path, etc. Make it so someone could follow along and find the same issue.
D. Proof of Concept (PoC):
Include screenshots, terminal output, file snippets — whatever backs your claim. Just remember to blur or redact any personal or sensitive data.
E. Impact:
Why should they care? Talk about what an attacker could do with this — access data, impersonate users, escalate privileges, etc.
F. Suggested Fix:
Help them out. Recommend removing the file, rotating credentials, restricting access, or implementing better secrets management.
💡 Pro Tip:
A clear, respectful, and thorough report increases your chances of a fast response and a higher bounty. Always stay professional and helpful — it builds a good rep with the program owners.
When you’re digging through exposed files or documents, not everything will be useful — but certain clues tend to stand out. These are the types of vulnerabilities you should keep an eye out for:
Hardcoded Credentials
These are things like API keys, database passwords, or tokens left directly inside config files or source code.
A. Why it matters: If these keys are valid, they could let you access private systems or data.
B. Tip: Look for terms like API_KEY, DB_PASSWORD, SECRET, or even full credential blocks in .env or .json files.
Unprotected Endpoints
Sometimes you’ll spot links or routes (like /admin, /api/private) that aren’t supposed to be public.
A. Why it matters: Without proper authentication, these could be entry points for exploitation (e.g., IDOR, broken access control).
B. Tip: JS files or manuals often mention these hidden gems.
Misconfigured Permissions
This happens when files, folders, or services are accessible to the public — even though they shouldn’t be.
A. Why it matters: It’s like leaving the door unlocked. Anyone can access what’s inside.
B. Tip: Look for open S3 buckets, open directories, or config files without access controls.
Outdated Technologies
Files might reference versions of frameworks, plugins, or platforms that are way out-of-date.
A. Why it matters: If those versions have known vulnerabilities (CVEs), it gives you a legitimate path to escalate.
B. Tip: Search PDFs, changelogs, or README files for version numbers like “Apache 2.4.29” or “jQuery 1.7”.
Data Leakage
Sometimes files unintentionally reveal personal or internal information — think customer names, emails, internal IPs, or even chat logs.
A. Why it matters: This kind of exposure can often be a bounty-worthy finding, especially if it involves sensitive or regulated data.
B. Tip: Scan .csv, .log, and .txt files closely. Even employee handbooks can leak insights.
Bug bounty platforms reward based on how serious and impactful your finding is. The more risk it poses to the company or its users, the higher the payout. Here’s a simple breakdown:
🟢 Low Severity ($50–$500)
These are smaller issues that still matter — like finding outdated software versions or publicly exposed non-sensitive files.
Example: You discover a PDF manual that mentions an old version of Apache. It’s not dangerous on its own, but it’s still worth reporting.
🟡 Medium Severity ($500–$2,000)
Things start getting more interesting — maybe you find API keys, backup files, or exposed endpoints that aren’t properly secured.
Example: You locate a GitHub repo with a working API token that can access limited data. That’s a solid medium.
🔴 High / Critical Severity ($2,000–$10,000+)
This is where the real money comes in. If your discovery could lead to account takeovers, sensitive data exposure, or remote code execution, you’re looking at top-tier rewards.
Example: You stumble across a public .env file that contains live database credentials—and those credentials give you access to customer data. That’s a critical issue, and a major payout.
Even simple mistakes like a forgotten config file can turn into gold if you know what to look for and how to report it properly.
These tips will help you get started the right way and avoid common pitfalls:
📌 Stay in Scope
Always stick to what’s allowed in the program’s rules. That usually means analyzing files from approved domains like *.target.com. Going beyond that can get you disqualified—or worse, banned.
🤝 Be Ethical
Your goal is to find and report, not to break things. Once you prove the vulnerability exists, stop there. Don’t exploit it further just to make it look more serious.
🌱 Start Small
If you’re new to this, look for bug bounty programs with wide scopes — especially wildcard targets like *.example.com. They’re more likely to have exposed stuff lying around.
📚 Learn from Others
One of the best ways to grow is by reading public write-ups from successful hunters. Platforms like HackerOne, Medium, and even GitHub have tons of examples showing how file analysis led to real bounties.
Subscribe to me on Medium and be sure to turn on email notifications so you never miss out on my latest walkthroughs, write-ups, and other informative posts.
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