Security Implications of CORS

CORS is crucial for web security but needs careful configuration to avoid potential vulnerabilities:

• Origin Verification: Only allow trusted origins. Allowing all origins ('*') can expose your API to risks like data leaks or misuse.
• Credentials and Cookies: When credentials is set to true, ensure the server’s Access-Control-Allow-Origin header is not set to '*'. It must be a specific origin.

const corsOptions = { origin: 'http://example.com', credentials: true, };

• Exposing Sensitive Headers: Be cautious when exposing headers using Access-Control-Expose-Headers. Only expose headers that are necessary and non-sensitive.

const corsOptions = { exposedHeaders: ['Content-Type', 'Authorization'], };

• HTTP Methods: Restrict the allowed methods to only those required by your application. This limits potential attack vectors.

const corsOptions = { methods: 'GET,POST,PUT,DELETE', };