LibreOffice and OpenOffice Java Flaw Enables Silent Code Execution via Malicious Spreadsheets

Security researchers have shown that a malicious spreadsheet can cause LibreOffice and Apache OpenOffice to execute attacker code automatically when the file is opened, without the usual macro warnings. The attack vector exploits Java support integrated into the office suites. According to the demonstration, the malicious file runs code silently as soon as it is opened, provided Java is enabled. As of the demonstration in October 2026, there are no confirmed reports of this flaw being used in the wild. The researchers emphasized that the attack is a proof-of-concept and no in-the-wild exploitation has been reported. Mitigation guidance recommends disabling Java support within LibreOffice and Apache OpenOffice settings as a temporary measure until further patches or updates are released by The Document Foundation and the Apache Software Foundation.