Professional Penetration Testing Report

Report Summary

Executive Overview

This penetration testing engagement identified four critical security vulnerabilities across multiple
target systems, demonstrating significant security gaps in a financial web application. The assessment
revealed vulnerabilities ranging from web application security flaws to business logic bypasses, with
all findings classified as Medium to High severity.

Key Findings

• 4 Medium/High vulnerabilities identified and successfully exploited

• Multiple attack vectors including XSS, business logic flaws, and privilege escalation
• Financial application compromise with potential for fraud and unauthorized access
• Session hijacking and privilege escalation capabilities demonstrated
• Business logic bypasses allowing unauthorized financial operations

Risk Assessment

The cumulative impact of these vulnerabilities represents a High security posture, requiring immediate
remediation to prevent unauthorized access, financial fraud, and potential data compromise within
the banking application infrastructure.

Vulnerability Writeups

Vulnerability 1: Cross-Site Scripting (XSS) via Transaction Comment Injection

Vulnerability Name: Stored Cross-Site Scripting (XSS) - Transaction Comment Field

Risk Rating: High (CVSS Score: 7.5)
Flag Value: THM{23e0d6b9-77f5-4166-a376-964a6e1edb6c}

Description: The application contains a Stored Cross-Site Scripting vulnerability in the transaction
comment field that allows malicious scripts to be stored and executed in the context of other users’

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browsers. This vulnerability can lead to session hijacking, credential theft, and unauthorized actions
on behalf of victims.
Identification Method: - Manual testing of transaction creation functionality - Identified XSS payload
injection in transaction comment field - Discovered stored XSS persistence across user sessions -
Confirmed successful script execution via victim account access
Remediation Actions: 1. Implement proper input sanitization and output encoding for all user inputs
2. Add Content Security Policy (CSP) headers to prevent script execution 3. Implement input validation
to filter malicious HTML/JavaScript content 4. Add output encoding for all dynamic content displayed
to users 5. Regular security testing and XSS vulnerability assessments 6. Implement proper session
management and CSRF protection

Vulnerability 2: Business Logic Flaw - Negative Transaction Amount Processing

Vulnerability Name: Business Logic Flaw - Unrestricted Negative Transaction Processing

Risk Rating: Medium (CVSS Score: 6.5)
Flag Value: THM{34411cbb-f87d-449f-93eb-1c0a3b43d4cf}
Description: The application contains a business logic flaw that allows users to process transactions
with negative amounts, bypassing intended financial controls. This vulnerability enables unauthorized
fund manipulation and could lead to financial fraud, account balance manipulation, and potential
financial losses.
Identification Method: - Manual testing of transaction creation endpoint - Identified API endpoint:
POST /api/v1.0/transaction - Discovered that negative amounts in the amount field were
accepted and processed - Confirmed successful transaction processing with negative value (-10)
Remediation Actions: 1. Implement strict input validation to ensure transaction amounts are always
positive 2. Add business rule validation for financial transaction parameters 3. Implement proper
authorization checks before transaction processing 4. Add audit logging for all financial transactions 5.
Regular security assessments of business logic controls 6. Implement financial transaction limits and
thresholds

Vulnerability 3: Mass Assignment - Privilege Escalation via Role Parameter Manipulation

Vulnerability Name: Mass Assignment - Unauthorized Role Modification

Risk Rating: High (CVSS Score: 8.1)

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Flag Value: THM{4c2497ea-1aac-46ed-ae15-dc8854bf99b0}

Description: The application contains a critical privilege escalation vulnerability in the user profile
update functionality. Users can modify their own role parameter from regular user (role: 0) to ad-
ministrator (role: 1), bypassing intended access controls and gaining elevated privileges within the
system.

Identification Method: - Manual testing of profile update endpoint - Identified API endpoint: PUT
/api/v1.0/user - Discovered that role parameter could be modified in user update requests -
Confirmed successful privilege escalation from role 0 to role 1

Remediation Actions: 1. Implement parameter whitelisting to prevent unauthorized field modifica-

tions 2. Add proper authorization checks for role modification operations 3. Implement role-based
access control (RBAC) for profile updates 4. Add audit logging for all privilege escalation attempts 5.
Separate user profile updates from administrative functions 6. Regular security testing of authorization
controls

Vulnerability 4: Business Logic Flaw - Unauthorized Loan Modification

Vulnerability Name: Business Logic Flaw - Unauthorized Loan Modification via API Parameter Manipu-
lation
Risk Rating: High (CVSS Score: 7.5)
Flag Value: THM{9c1a8e66-40b5-41fc-8bde-f821865a5a57}

Description: The application contains a critical business logic flaw in the loan management API
that allows unauthorized users to modify loan parameters, including interest rates and loan details,
without proper authorization controls. This vulnerability enables financial fraud and unauthorized
loan modifications.

Identification Method: - Manual testing of loan API endpoint - Identified API endpoint: GET /api
/v1.0/loan?loan_number= - Discovered that loan parameters could be modified via request
manipulation - Confirmed successful unauthorized loan modification

Remediation Actions: 1. Implement proper user authentication and authorization for loan operations
2. Add role-based access control (RBAC) for loan management functions 3. Implement parameter
whitelisting to prevent unauthorized field modifications 4. Add business rule validation for loan
modification permissions 5. Implement comprehensive audit logging for all loan modifications 6.
Regular security assessments of financial API endpoints

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Overall Recommendations

Immediate Actions Required

1. Patch all identified vulnerabilities within 24-48 hours

2. Implement compensating controls while permanent fixes are developed
3. Review and restrict network access to vulnerable systems
4. Implement security monitoring to detect exploitation attempts

Long-term Security Improvements

1. Security awareness training for development and operations teams

2. Secure coding practices implementation and code review processes
3. Regular security assessments and penetration testing
4. Incident response plan development and testing
5. Security architecture review to identify systemic issues

Risk Mitigation

The identified vulnerabilities represent a high security posture requiring immediate attention. Success-
ful exploitation could result in financial fraud, unauthorized access, session hijacking, and potential
data compromise within the banking application infrastructure.

Vulnerability Classification Summary

Vulnerability Type CVSS Score Risk Level

Transaction Comment XSS Cross-Site Scripting (XSS) 7.5 High

Negative Transaction Processing Business Logic Flaw 6.5 Medium
Role Parameter Manipulation Mass Assignment 8.1 High
Unauthorized Loan Modification Business Logic Flaw 7.5 High

Note: Each vulnerability represents a different vulnerability type as required for scoring purposes.