Other users can watch your browsing and time your keystrokes through OS file notifications

Researchers at Graz University of Technology have used the file-notification systems in Windows, Linux, and macOS to spy on activity in other accounts. On Windows, a standard unprivileged account detected 95.7 percent of another user’s visits to popular websites in Firefox, and every site it flagged was one the victim’s browser had loaded. On Linux, a separate weakness exposed keystroke timing, both at the local keyboard and in SSH sessions.