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Security researchers from Graz University of Technology in Austria have discovered significant vulnerabilities in the file notification systems of major operating systems: Android, Linux, macOS, and Windows. These flaws have existed for decades and can lead to the leakage of sensitive system information. The affected systems include inotify on Linux (since 2005), FileObserver on Android (since 2008), ReadDirectoryChangesW on Windows (since 2000), and FSEvents on macOS (since 2007). The vulnerabilities allow unprivileged users to monitor file events without explicit read permissions, enabling potential attacks such as inter-keystroke timing attacks and website fingerprinting. For example, on Linux, monitoring a readable directory can leak events on files that cannot be read, allowing attackers to achieve a 93.1% to 100% accuracy rate in monitoring keystrokes. Specific vulnerabilities include CVE-2025-68788 on Linux, which received a partial fix in December 2025, and issues on Android where FileObserver can bypass app storage isolation. On macOS, limited information is available due to a lack of bypasses for private directories, while on Windows, monitoring the root directory can reveal the full path of every accessed file, allowing real-time tracking of web activity with a 97.8% accuracy rate. Microsoft has described the issue as "by-design," which has faced criticism. The researchers propose stronger mitigations, such as disallowing monitoring of entire drives on Windows and introducing a permission system for file monitoring on Windows and macOS. Their findings will be presented at the ACM CCS 2026 conference in November in The Hague, Netherlands.