A cross-site scripting vulnerability is present in the hotspot of MikroTik's RouterOS on versions below 7.19.2. An attacker can inject the `javascript` protocol in the `dst` parameter. When the victim browses to the malicious URL and logs in, the XSS executes. The POST request used to login, can also be converted to a GET request, allowing an attacker to send a specifically crafted URL that automatically logs in the victim (into the attacker's account) and triggers the payload.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.