Vendor Penetration Test Findings Examples

Most vendor penetration tests reveal authentication bypasses, unpatched vulnerabilities, and exposed APIs that create direct paths into your environment. Critical findings typically include hardcoded credentials (found in some tests), SSRF vulnerabilities allowing internal network access, and inadequate segmentation between customer environments.

Key takeaways:

• Authentication and authorization flaws represent a significant number of critical findings
• Supply chain attacks often exploit API misconfigurations and weak OAuth implementations
• Unpatched systems averaging 180+ days behind current versions appear in a large share of vendor pen tests
• Multi-tenant architecture flaws can expose your data through other customers' vulnerabilities
• Post-test remediation verification catches many regression rate in vendor fixes

Your vendor's security posture directly impacts your attack surface. When penetration testing reveals critical vulnerabilities in third-party systems, the findings often paint a stark picture: vendors operating production systems with the same security gaps that internal teams patched years ago.

Real vendor penetration test results show patterns every TPRM manager recognizes. Authentication bypasses that grant admin access. APIs leaking customer data across tenant boundaries. Remote code execution through unpatched dependencies. These aren't theoretical risks—they're active vulnerabilities discovered during routine assessments.

The examples below come from actual vendor penetration tests across SaaS platforms, managed service providers, and critical infrastructure vendors. Names and identifying details have been changed, but the vulnerabilities, remediation timelines, and business impacts reflect real assessments conducted between 2021-2024.

Case Study: Financial Data Processor Authentication Bypass

A payment processing vendor serving 200+ financial institutions underwent penetration testing after expanding their API gateway. The vendor processed $2.3B in monthly transactions and maintained SOC 2 Type II certification.

Initial Findings

The penetration test uncovered a critical authentication bypass in their newer API endpoints:

Vulnerability Details:

• JWT tokens accepted with alg: none header
• Session cookies remained valid for 30 days after password changes
• API rate limiting only applied to failed attempts, not successful ones
• Debug endpoints exposed in production returning full stack traces

Attack Scenario Demonstrated:

1. Attacker modifies JWT algorithm to "none"
2. Crafts token with arbitrary user_id claim
3. Accesses any customer's transaction history
4. Exports data through unlimited API calls

The vendor's own monitoring showed zero alerts during the simulated attack. Their SIEM rules looked for failed authentications but ignored successful requests with modified tokens.

Remediation Journey

Initial vendor response claimed the finding was "theoretical" since they hadn't seen exploitation. After demonstrating data extraction from their largest customer's test environment, remediation priority changed.

Week 1-2: Emergency patches for JWT validation Week 3-4: Session management overhaul
Week 5-8: API gateway replacement Week 9-12: Full re-architecture of authentication layer

Total remediation time: 97 days for all critical findings.

Multi-Tenant Data Isolation Failures

Background: SaaS Provider Serving Healthcare

A healthcare SaaS platform underwent penetration testing during vendor onboarding for a major hospital system. The vendor stored PHI for 1,200 healthcare providers and claimed HIPAA compliance.

Critical Findings

Cross-Tenant Data Access:

• URL manipulation allowed viewing other customers' patient records
• Incremental object IDs without access validation
• Shared encryption keys across all tenants
• Backup restoration process mixed customer data

Technical Deep Dive:

The application used MongoDB with a single database for all customers. Tenant isolation relied solely on application-layer filtering:

// Vulnerable query pattern found
db.patients.find({ _id: request.params.id })
// Missing tenant validation

Penetration testers accessed 15 different customers' data by incrementing URL parameters. The vendor's logging showed these as "successful retrievals" without any indication of unauthorized access.

Business Impact

• 14-month remediation timeline due to database re-architecture
• $1.2M development costs passed to customers through price increases
• 3 customers terminated contracts during remediation
• HIPAA audit triggered for all affected entities

API Security Configuration Cascade

Vendor Profile: Cloud Infrastructure Provider

A cloud backup vendor underwent testing after several customers reported suspicious access patterns. The vendor managed 400TB of customer data across their multi-region infrastructure.

Discovery Timeline

Day 1: Enumerated 47 undocumented API endpoints Day 2: Found Swagger documentation at /api/v2/docs (no authentication) Day 3: Identified customer API keys in JavaScript bundles Day 4: Achieved remote code execution through SSRF vulnerability Day 5: Demonstrated lateral movement to customer backup storage

Key Vulnerabilities

1. Exposed Internal APIs

   • GraphQL introspection enabled in production
   • Admin endpoints accessible without authentication
   • API keys embedded in client-side code

2. SSRF to RCE Chain

   • Webhook functionality accepted internal URLs
   • Metadata service accessible at 169.254.169.254
   • IAM roles allowed S3 bucket access

3. Backup Encryption Issues

   • Master keys stored in same S3 buckets as backups
   • Key rotation hadn't occurred in 3 years
   • Deleted customer data retained indefinitely

Vendor Response Patterns

The vendor's remediation approach revealed common organizational issues:

• Security team had 2 people for 50 developers
• No security review process for new features
• Penetration test was their first in 4 years
• Compliance certifications obtained through questionnaires only

Unpatched Dependency Exploitation

Case: Marketing Automation Platform

A marketing automation vendor serving 5,000 SMBs failed penetration testing due to systematically unpatched systems.

Vulnerability Inventory

Operating System: Ubuntu 16.04 (EOL April 2021) Framework: Spring Boot 1.5.x with 42 known CVEs Database: PostgreSQL 9.6 (EOL November 2021) Dependencies: 234 outdated packages, 67 with critical vulnerabilities

Exploitation Path

1. CVE-2022-22965 (Spring4Shell) provided initial access
2. Privilege escalation through outdated kernel
3. Database credentials in plain text configuration files
4. Lateral movement to all customer instances

The vendor claimed their WAF prevented exploitation. Penetration testers bypassed it in 15 minutes using URL encoding.

Risk Quantification

• 180,000 customer records accessible
• Complete infrastructure compromise possible
• 18-month old vulnerabilities actively exploitable
• No evidence of security patching process

Common Patterns Across Vendor Penetration Tests

After reviewing 50+ vendor penetration test reports, clear patterns emerge:

Technical Debt Indicators

1. Authentication/Authorization (a significant number of critical findings)

   • Broken OAuth implementations
   • Session fixation vulnerabilities
   • Missing function-level access controls

2. Data Exposure (a substantial portion of critical findings)

   • Verbose error messages with stack traces
   • Directory traversal in file operations
   • Unencrypted data in transit between services

3. Infrastructure Security (some critical findings)

   • Exposed management interfaces
   • Default credentials on internal services
   • Missing network segmentation

Organizational Indicators

High-Risk Vendor Characteristics:

• Security team ratio below 1:25 (security:developers)
• Last penetration test more than 2 years ago
• Compliance achieved through self-attestation only
• No dedicated AppSec or DevSecOps function
• Remediation SLAs exceeding 90 days for critical findings

Continuous Monitoring Integration

Penetration test findings should feed directly into your continuous monitoring program:

Monitoring Automation Requirements

1. API Security Posture

   • Weekly endpoint enumeration
   • Authentication mechanism changes
   • New subdomain detection

2. Patch Management Verification

   • CVE correlation with vendor stack
   • Public vulnerability disclosure monitoring
   • Version detection through fingerprinting

3. Configuration Drift Detection

   • TLS certificate monitoring
   • DNS record changes
   • Open port modifications

Risk Scoring Adjustments

Post-penetration test risk scoring typically shifts:

• Critical findings: Immediate tier elevation
• Remediation delays: 10-point risk score increase per month
• Repeat findings: Vendor relationship review trigger

Compliance Framework Mapping

SOC 2 Control Failures

Common penetration test findings map to SOC 2 control failures:

CC6.1 (Logical Access Controls): Authentication bypasses CC6.6 (Encryption): Weak cryptographic implementations
CC7.1 (Vulnerabilities): Unpatched systems CC7.2 (System Monitoring): Missing security event detection

ISO 27001 Gaps

A.12.6.1: Missing vulnerability management A.13.1.3: Inadequate network segregation A.14.2.9: Absent security testing in SDLC A.18.2.3: Failure to meet contractual security requirements

Frequently Asked Questions

How often should critical vendors undergo penetration testing?

Critical vendors should complete penetration testing annually, with high-risk vendors tested semi-annually. Any major architecture changes or security incidents should trigger additional testing.

What's the typical remediation timeline for critical penetration test findings?

Critical findings average 30-45 days for remediation, though complex architectural issues can extend to 90-180 days. Your contracts should specify maximum remediation timelines with penalties for delays.

Should we require vendors to share full penetration test reports?

Yes, require full reports under NDA rather than summary letters. Executive summaries often omit critical technical details needed for risk assessment. At minimum, obtain vulnerability details, CVSS scores, and evidence screenshots.

How do we validate vendor remediation claims?

Require retest reports from the same penetration testing firm. a significant number of "fixed" vulnerabilities return due to incomplete remediation. For critical vendors, consider funding independent verification testing.

What penetration testing standards should we require?

Mandate PTES (Penetration Testing Execution Standard) or OWASP Testing Guide methodology. Require testing from firms with CREST or similar accreditation. Specify minimum testing duration based on vendor complexity.

Can we perform our own penetration tests on vendor systems?

Only with explicit written authorization. Most vendor contracts prohibit customer-initiated testing. Instead, negotiate "right to test" clauses during contract renewal or mandate specific testing requirements.

What's the minimum acceptable penetration testing scope?

External infrastructure, authenticated application testing, and API security assessment. For critical vendors, add cloud configuration reviews, source code analysis, and social engineering scenarios.