Description

Detects when unsanitized user-controlled input is written into Winston log messages in JavaScript applications. Without proper sanitization, attackers can inject newline characters or forged log entries into the log stream, misleading security monitoring systems and hiding malicious activity.

Detection Strategy

• Identifies calls to Winston logger methods (info, error, warn, debug, fatal, trace, log)

• Resolves the logger instance back to its definition to confirm it was created via winston.createLogger()

• Inspects the arguments passed to the log call for symbols, element accesses, or member accesses that originate from HTTP request data

• Reports a vulnerability when user-controlled input reaches a Winston log method without sanitization or validation

Vulnerable code example

const winston = require('winston');

const logger = winston.createLogger({
  transports: [new winston.transports.Console()]
});

app.get('/login', (req, res) => {
  const username = req.query.username;...

✅ Secure code example

const winston = require('winston');

const logger = winston.createLogger({
  transports: [new winston.transports.Console()]
});

app.get('/login', (req, res) => {
  const username = req.query.username;...