Course

In this lab, you are provided with a TypeScript snippet that implements basic authentication using Express.js. The goal is to identify the security vulnerability present in the code. The code imports necessary modules from Express, creates an application instance, and defines a middleware function, `basicAuth`, which checks for the presence of an authorization header, decodes it, and verifies the username and password against environment variables.

The critical issue lies in the logical error within the authentication check. The code incorrectly uses an 'or' condition (`||`) instead of an 'and' condition (`&&`). This flaw allows an attacker to authenticate with just a valid username or password, making the system vulnerable to unauthorized access. The video explains this vulnerability in detail and highlights the importance of correct logical conditions in security checks.