Have Firefox blocked this and/or are there ways users can protect themselves? "14 new types of 'XS-Leak' cross-site leak attacks against modern web browsers, including Google Chrome, Microsoft Edge, Safari, and Mozilla Firefox." "These types of side-channel attacks are called 'XS-Leaks,' and allow attacks to bypass the 'same-origin' policy in web browsers so that a malicious website can steal info in the background from a trusted website where the user enters information. "The principle of an XS-Leak is to use such side-channels available on the web to reveal sensitive information about users, such as their data in other web applications, details about their local environment, or internal networks they are connected to," explains the XS-Leaks wiki. For example, an XS-Leak attack could help a background site siphon the email inbox contents from an active tab used for accessing webmail." https://www.bleepingcomputer.com/news/security/researchers-discover-14-new-data-stealing-web-browser-attacks/