Concurrent Login Security: How to Check Whether Multiple Sessions Are Allowed (opens in new tab)

Why unlimited logins can become a hidden business logic vulnerability. Imagine This Scenario A user logs into your application from their laptop. A few seconds later, the same account logs in from another browser. Then another device. And another. Everything still works. At first glance, this seems harmless. After all, many modern applications support multiple devices. But here's the catch: Should every application allow unlimited concurrent sessions? Not always. In some systems, allowing mul...