UC Browser for Android (package com.UCMobile.intl, version 13.7.8.1314) contains a Universal Cross-Site Scripting vulnerability that allows an attacker to execute arbitrary JavaScript in the context of any origin. An attacker hosts a specially crafted URL on a UC-owned domain (via a reflected XSS) that leverages the browser's internal JavaScript bridge to register a deferred callback, navigate the tab to a victim site, and then execute attacker-controlled code on that site when a login dialog is dismissed.
https://gist.github.com/OmriInbar-Novee/ef7a92db148b2eb1ab0aa7b99a565c4c
https://gist.github.com/OmriInbar-Novee/9fd65fe08c1b1cff6a19350e44425de2