Back to Vulnerability Database

Insertion of Sensitive Information Into Sent Data

Description

Insertion of Sensitive Information Into Sent Data occurs when code transmits data to another actor but inadvertently includes sensitive information that should not be accessible to the recipient. This can happen through improper data handling, incorrect API responses, debug information in production, or failure to strip sensitive fields before transmission. The sensitive information may include credentials, personal data, internal system details, session tokens, or other data that could be misused by the receiving party.

Risk

This vulnerability directly compromises confidentiality by transmitting sensitive data to unintended recipients. In web applications, sensitive data may be included in API responses accessible to end users or third parties. In networked systems, data meant for internal use may be transmitted over public channels. The impact ranges from privacy violations (exposing user data) to complete system compromise (exposing credentials or tokens). For e-commerce and financial systems, exposure of customer transactional data leads to regulatory violations and fraud. WordPress and other CMS platforms are frequently affected due to complex plugin ecosystems.

Solution

Implement strict output filtering that removes sensitive fields before data transmission. Use data transfer objects (DTOs) that contain only the fields intended for transmission rather than serializing internal objects directly. Apply the principle of least privilege to API responses—return only the minimum data necessary. Implement proper access controls to verify recipients are authorized for all data being sent. Remove debug and diagnostic information in production. Conduct security reviews of all data transmission points.

Common Consequences

ImpactDetails
ConfidentialityScope: Information Disclosure

Sensitive information transmitted to unauthorized parties, including credentials, personal data, or business secrets.
Access ControlScope: Unauthorized Access

Exposed credentials or session tokens enable attackers to gain unauthorized system access.
ComplianceScope: Regulatory Violation

Transmission of protected data (PII, PHI, payment data) violates GDPR, HIPAA, PCI-DSS requirements.

Example Code + Solution Code

Vulnerable Code

# VULNERABLE: Serializing entire user object
@app.route('/api/user/<id>')
def get_user(id):
    user = User.query.get(id)
    # Sends ALL fields including password hash, internal IDs
    return jsonify(user.__dict__)

# VULNERABLE: Including debug data in response
@app.route('/api/order/<id>')
def get_order(id):
    order = Order.query.get(id)
    return {
        "order": order.to_dict(),
        "internal_cost": order.internal_cost,  # Business sensitive
        "supplier_id": order.supplier_id,      # Internal reference
        "debug_trace": request.environ         # System internals
    }

// VULNERABLE: Embedding sensitive data in client-side code
function loadUserData(userId) {
    const userData = {
        id: userId,
        name: 'John Doe',
        email: '[email protected]',
        apiKey: 'sk_live_abc123xyz',  // Exposed to client!
        internalId: 'INT-12345'       // Internal reference exposed
    };
    return userData;
}

// VULNERABLE: Error response with sensitive info
app.get('/api/resource', (req, res) => {
    try {
        // ... operation
    } catch (err) {
        res.status(500).json({
            error: err.message,
            connectionString: process.env.DATABASE_URL,  // Credentials!
            stack: err.stack
        });
    }
});

Fixed Code

from dataclasses import dataclass

# SAFE: Use DTO with only public fields
@dataclass
class UserDTO:
    id: int
    name: str
    email: str

    @classmethod
    def from_user(cls, user):
        return cls(id=user.id, name=user.name, email=user.email)

@app.route('/api/user/<id>')
def get_user_safe(id):
    user = User.query.get(id)
    if not user:
        return {"error": "User not found"}, 404

    # Return only public fields via DTO
    dto = UserDTO.from_user(user)
    return jsonify(asdict(dto))

# SAFE: Explicit field selection
@app.route('/api/order/<id>')
def get_order_safe(id):
    order = Order.query.get(id)
    if not order:
        return {"error": "Order not found"}, 404

    # Return only customer-facing data
    return {
        "order_id": order.public_id,
        "status": order.status,
        "items": [item.to_public_dict() for item in order.items],
        "total": order.total
    }

// SAFE: Separate public and private data
function loadUserDataSafe(userId) {
    // Only public data sent to client
    return {
        id: userId,
        name: 'John Doe',
        displayEmail: 'j***@example.com'  // Masked
    };
    // API keys and internal IDs stay server-side
}

// SAFE: Generic error responses
app.get('/api/resource', (req, res) => {
    try {
        // ... operation
    } catch (err) {
        // Log detailed error internally
        console.error('Resource error:', err);

        // Return generic message to client
        res.status(500).json({
            error: 'An error occurred processing your request',
            requestId: generateRequestId()  // For support reference only
        });
    }
});

// SAFE: Middleware to strip sensitive fields
function sanitizeResponse(data) {
    const sensitiveFields = ['password', 'apiKey', 'internalId', 'ssn', 'creditCard'];
    const sanitized = { ...data };

    sensitiveFields.forEach(field => {
        delete sanitized[field];
    });

    return sanitized;
}

Exploited in the Wild

WordPress Core Information Exposure (WordPress, 2025)

CVE-2025-58246 allows attackers with contributor-level privileges to retrieve embedded sensitive data that should not be exposed through WordPress's REST API, affecting millions of WordPress installations.

WooCommerce Wallet System (WooCommerce, 2025)

CVE-2025-68029 in WP Swings Wallet System for WooCommerce exposes sensitive customer and transactional data through improper handling of outbound communications.

Windows Speech Service (Microsoft, 2025)

CVE-2025-59509 causes Windows Speech service to inadvertently include sensitive information in transmitted data, enabling local attackers to access unauthorized information.

Tools to test/exploit

  • Burp Suite — intercept and analyze API responses for sensitive data.

  • OWASP ZAP — automated scanning for information in responses.

  • Postman — API testing to verify response contents.

CVE Examples

References

  1. MITRE. "CWE-201: Insertion of Sensitive Information Into Sent Data." https://cwe.mitre.org/data/definitions/201.html

  2. OWASP. "API Security Top 10." https://owasp.org/www-project-api-security/