LINE client for iOS prior to 15.4 allows man-in-the-middle attacks due to improper SSL/TLS certificate validation in an integrated financial SDK. The SDK interfered with the application's network processing, causing server certificate verification to be disabled for a significant portion of network traffic, which could allow a network-adjacent attacker to intercept or modify encrypted communications.

LINE client for iOS prior to 15.19 allows UI spoofing due to inconsistencies between the navigation state and the in-app browser's user interface, which could create confusion about the trust context of displayed pages or interactive elements under specific conditions.

LINE client for Android versions from 13.8 to 15.5 is vulnerable to UI spoofing in the in-app browser where a specific layout could obscure the full-screen warning prompt, potentially allowing attackers to conduct phishing attacks.

The in-app browser in LINE client for iOS versions prior to 14.14 is vulnerable to address bar spoofing, which could allow attackers to execute malicious JavaScript within iframes while displaying trusted URLs, enabling phishing attacks through overlaid malicious content.