Form Filling Security: How We Keep Your Data Safe
A transparent look at our privacy-first architecture and the security measures that protect your sensitive information. Learn exactly how we keep your data safe with field-level encryption, modern authentication, and multiple layers of protection.
When you trust Fyllyo with your passport numbers, Social Security numbers, and other sensitive information, you deserve complete transparency about how we protect it. This is a technical deep dive into our actual security implementation—what we've built, how it works, and how we keep improving.
The Stakes Are High
Form filling tools handle the most sensitive data imaginable. A security breach isn't just inconvenient—it can ruin lives. That's why we built Fyllyo with security as the foundation, not an afterthought.
Our Core Security Principle: Privacy-First Architecture
We built Fyllyo with security and privacy at its core. Your sensitive data is protected with multiple layers of encryption, modern authentication, and strict access controls.
Field-Level Encryption
Highly sensitive PII like SSN and passport numbers use per-user encryption keys with AES-256-GCM before storage.
Secure Authentication
Google OAuth 2.0 with PKCE ensures secure login without us ever seeing your password.
No Analytics on Personal Data
We collect usage analytics, but never on the content of your forms or personal information.
Encrypted Storage
All data is encrypted at rest in our database and in transit using TLS 1.3.
Technical Deep Dive: How It Actually Works
1. Authentication & Token Security
We use Google OAuth 2.0 with PKCE (Proof Key for Code Exchange) for secure authentication. Your access tokens are short-lived and automatically refresh in the background. In the browser extension, tokens are encrypted with AES-256-GCM before storage.
Login → Google OAuth 2.0 with PKCE → Encrypted Token Storage
Web App: HttpOnly cookies prevent JavaScript access
Extension: AES-256-GCM encrypted local storage2. Field-Level Encryption for Sensitive Data
Your most sensitive information (Social Security numbers, passport numbers) receives an extra layer of protection. We generate a unique encryption key for each user and encrypt these fields separately before storing them in our database.
Highly sensitive PII: Per-user key → AES-256-GCM → Database
In transit: All communications use TLS 1.3
3. AI Processing & Data Minimization
When our AI analyzes forms, we only send the necessary context to generate accurate fills. We partner with OpenAI for AI processing, and your data is not stored on their servers or used for training their models.
🔐 Technical Note
We implement prompt injection prevention to protect against malicious inputs that could manipulate our AI system. All inputs are validated and sanitized before processing.
What Data We Do Collect (And Why)
Transparency means being honest about what we do collect. Here's the complete list:
Email address, encrypted password hash, account creation date
Why: To verify your identity and protect your account
Which features you use, how often, error rates, performance metrics
Why: To improve the product and fix bugs
Field types, labels, and website domains (but never the values you enter)
Why: To train our AI to recognize new form types
⚠️ What We Never Collect
- • Your actual form data (names, addresses, SSNs, etc.)
- • Screenshots or recordings of your screen
- • Browsing history outside of form interactions
- • Passwords or login credentials for other sites
- • Financial information or payment details
Security Measures Beyond Encryption
Application Security
- Rate limiting with progressive account lockout to prevent brute force attacks
- CSRF protection with session-bound tokens for all state-changing operations
- CORS configuration with strict origin whitelisting
- Input validation using Pydantic schemas for all API endpoints
- Prompt injection prevention to protect against AI manipulation
File Upload Security
- MIME type validation and magic number verification of actual file content
- File size limits to prevent resource exhaustion
- Suspicious content detection (scripts, executables) with automatic rejection
- Streaming upload validation for large files
- Automatic cleanup of failed or incomplete uploads
Logging & Monitoring
- Structured logging for all security events and API requests
- Audit trail with database-backed event tracking
- Sensitive data sanitization in logs (no passwords or PII)
- Failed authentication tracking and alerting
Browser Extension Security
- Minimal permissions requested (only required browser APIs)
- Encrypted token storage with automatic cleanup on logout
- Type-safe message passing between extension components
- Origin validation for all cross-component communication
Privacy Compliance & Your Rights
We take data protection regulations seriously and have implemented comprehensive compliance measures to protect your rights.
🇪🇺 GDPR Compliant
Full compliance with European data protection regulations.
- • Right to access your data
- • Right to rectification
- • Right to erasure (delete account)
- • Right to data portability
🇺🇸 CCPA Compliant
California Consumer Privacy Act compliance.
- • Know what data we collect
- • Request data deletion
- • We don't sell your data
- • No discrimination for exercising rights
Your Data, Your Control
You can export all your data in a portable format or permanently delete your account at any time through the settings panel. We'll process deletion requests promptly and confirm when complete.
Security Commitment & Incident Response
We take security seriously and are committed to protecting your data:
🛡️ Defense in Depth
Your most sensitive data (SSN, passport numbers) uses field-level encryption with per-user keys. Even if someone gained unauthorized database access, they would only see encrypted data. Combined with our authentication controls and rate limiting, we've built multiple layers of protection around your information.
Your Role in Security
Security is a partnership. Here's how you can protect yourself:
- Use a strong Google account password: Your Fyllyo account is protected by Google OAuth
- Enable two-factor authentication on Google: Adds critical protection to your account
- Keep your browser updated: Security patches are essential for extension security
- Be cautious on public WiFi: All our traffic uses TLS 1.3, but VPNs add extra protection
- Review your stored data regularly: Remove old or unnecessary information
- Report suspicious activity: Contact us immediately if you notice anything unusual
Transparency and Accountability
We believe in being transparent about our security practices:
- Clear privacy policy explaining exactly what data we collect and why
- Structured audit logging for accountability and security investigations
- GDPR and CCPA compliance with full data rights implementation
- Prompt communication if security incidents occur
- Regular security updates and improvements to our platform
Questions? We're Here to Help
Security shouldn't be a black box. If you have questions about our security practices, need clarification on any aspect of our data handling, or want to report a security concern, we're here to help.
We're committed to continuously improving our security. Your trust is our most valuable asset, and we take that responsibility seriously every day.