The in-app browser of LINE client for iOS versions below 14.9.0 contains a Universal XSS (UXSS) vulnerability. This vulnerability allows for cross-site scripting (XSS) where arbitrary JavaScript can be executed in the top frame from an embedded iframe on any displayed web site within the in-app browser. The in-app browser is usually opened by tapping on URLs contained in chat messages, and for the attack to be successful, the victim must trigger a click event on a malicious iframe. If an iframe embedded in any website can be controlled by an attacker, this vulnerability could be exploited to capture or alter content displayed in the top frame, as well as user session information. This vulnerability affects LINE client for iOS versions below 14.9.0 and does not affect other LINE clients such as LINE client for Android. Please update LINE client for iOS to version 14.9.0 or higher.