A vulnerability has been identified in LIFF SDK versions 2.20.0 through 2.31.0, where a DOM-based cross-site scripting (XSS) flaw allows an attacker to execute arbitrary JavaScript in the origin of an affected LIFF application's endpoint when a user opens a specially crafted URL in an external browser, potentially leading to disclosure of JavaScript-accessible authentication tokens or application data, or unauthorized actions using the user's session.