CVD Case Study: Critical Data Leak in Social Media Application
A responsible disclosure case that protected over 100,000 users from potential data exposure
Discovery
The vulnerability was discovered during routine personal use of a mobile social media application. As an active user of the platform, I was conducting traffic analysis using Proxyman to understand the application's data flow and network behavior.
The analysis revealed that a single user profile request was returning an unexpectedly large payload of approximately 7,800 lines of JSON. This immediately indicated a potential over-fetching issue that warranted deeper investigation.
Vulnerability Details
Application Context
The application was a niche social media platform with standard features including user profiles, follower/following relationships, content posting, commenting, and engagement metrics.
Security Issue
The server-side API was returning excessive information in response to profile requests. Instead of providing only the data necessary for UI rendering, the endpoint exposed:
- Personal Identifiable Information (PII): Real names and physical addresses
- Contact Information: Phone numbers and email addresses
- Financial Data: Payment information and subscription details
This represented a critical data leak as any authenticated user could potentially access sensitive information of other users through normal API interactions.
Response Timeline
Initial Discovery
Identified the vulnerability through traffic analysis during personal use of the application
Impact Assessment
Conducted thorough analysis to determine the scope of affected users (100,000+)
BSI Notification
Contacted the Federal Office for Information Security (BSI) with detailed findings
Documentation & Reproduction
Created comprehensive report with reproduction steps and assisted BSI with verification
Resolution
BSI forwarded the redacted report to the software manufacturer, leading to vulnerability remediation
Outcome
Through responsible disclosure and coordinated vulnerability disclosure (CVD) processes, the data leak was successfully closed, protecting over 100,000 users from potential data exposure.
The manufacturer implemented proper API security measures to ensure that endpoints only return necessary data based on user privileges and UI requirements, following the principle of least privilege.
This case was recognized by the BSI through inclusion in their Hall of Fame, acknowledging the importance of responsible security research in protecting digital infrastructure and user privacy.
Key Takeaways
- Regular security auditing and traffic analysis can reveal critical vulnerabilities in production systems
- Coordinated vulnerability disclosure through proper channels ensures effective remediation
- API endpoints should implement strict data filtering to prevent information leakage
- Responsible disclosure protects users while giving organizations time to remediate issues
Recognized by the German Federal Office for Information Security (BSI)
View BSI Hall of Fame