Horilla is a free and open source Human Resource Management System (HRMS). Prior to version 1.4.0, the file upload flow performs validation only in the browser and does not enforce server-side checks. An attacker can bypass the client-side validation (for example, with an intercepting proxy or by submitting a crafted request) to store an executable HTML document on the server. When an administrator or other privileged user views the uploaded file, the embedded script runs in their context and sends session cookies (or other credentials) to an attacker-controlled endpoint. The attacker then reuses those credentials to impersonate the admin. This issue has been patched in version 1.4.0.