# Insertion of Sensitive Information into Log File (CWE-532)

Information written to log files can be of a sensitive nature and give valuable guidance to an attacker or expose sensitive user information.

**Stack:** JavaScript

- Prevalence: Medium 3 languages covered
- Impact: High 1 high-severity rules
- Prevention: Documented 3 fix examples

**OWASP:** Security Logging and Monitoring Failures (A09:2021-Security Logging and Monitoring Failures) - #9

## Description

When sensitive information like passwords, tokens, or personal data is logged, it becomes accessible to anyone with access to the logs. Log files are often stored with less security than the data they contain.

## Prevention

Prevention strategies for Information Exposure Through Logs based on 1 Shoulder detection rules.

### JavaScript

Exclude sensitive fields from logged data using destructuring or redaction

## Warning Signs

- [MEDIUM] when user-provided sensitive data (passwords, tokens, API keys, secrets, etc

## Consequences

- Read Application Data
- Gain Privileges

## Mitigations

- Never log sensitive information such as passwords or tokens
- Implement log data classification and filtering
- Mask or redact sensitive data before logging

## Detection

- Total rules: 3
- Languages: go, javascript, typescript, python

## Rules by Language

### Javascript (1 rules)

- **Sensitive Data Exposure in Logs** [MEDIUM]: Detects when user-provided sensitive data (passwords, tokens, API keys, secrets, etc.)
flows directly into logging functions without proper redaction or masking.

This rule uses taint flow analysis to detect ACTUAL sensitive data being logged,
not just variables with sensitive names. Only triggers when:
1. Data originates from user input (req.body, req.headers, etc.)
2. Contains sensitive field names (password, token, secret, etc.)
3. Flows into logging functions without sanitization

Sensitive data in logs can lead to:
- Credential exposure in log files or monitoring systems
- Unauthorized access if logs are compromised
- Compliance violations (PCI-DSS, GDPR, HIPAA)
- Data breaches through log aggregation systems
  - Remediation: Exclude sensitive fields from logged data:

```javascript
const { password, ...safeBody } = req.body;
console.log('Request body:', safeBody);

function redactToken(token) {
  return token ? token.substring(0, 4) + '***' : '';
}
logger.info('Token:', redactToken(authToken));
```

Learn more: https://shoulder.dev/learn/javascript/cwe-532/sensitive-data-logging

### Typescript (1 rules)

- **Sensitive Data Exposure in Logs** [MEDIUM]: Detects when user-provided sensitive data (passwords, tokens, API keys, secrets, etc.)
flows directly into logging functions without proper redaction or masking.

This rule uses taint flow analysis to detect ACTUAL sensitive data being logged,
not just variables with sensitive names. Only triggers when:
1. Data originates from user input (req.body, req.headers, etc.)
2. Contains sensitive field names (password, token, secret, etc.)
3. Flows into logging functions without sanitization

Sensitive data in logs can lead to:
- Credential exposure in log files or monitoring systems
- Unauthorized access if logs are compromised
- Compliance violations (PCI-DSS, GDPR, HIPAA)
- Data breaches through log aggregation systems
  - Remediation: Exclude sensitive fields from logged data:

```javascript
const { password, ...safeBody } = req.body;
console.log('Request body:', safeBody);

function redactToken(token) {
  return token ? token.substring(0, 4) + '***' : '';
}
logger.info('Token:', redactToken(authToken));
```

Learn more: https://shoulder.dev/learn/javascript/cwe-532/sensitive-data-logging