![]() ![]() Inführ provided a proof-of-concept (PoC) video demonstration showing how he was able to trick the event into calling a specific function within a Python file, which eventually executed the researcher's payload through Windows command line (cmd) without showing any warning dialog to the user. To exploit this vulnerability, Inführ created an ODT file with a white-colored hyperlink (so it can't be seen) that has an "onmouseover" event to trick victims into executing a locally available python file on their system when placing their mouse anywhere on the invisible hyperlink.Īccording to the researcher, the python file, named "pydoc.py," that comes included with the LibreOffice's own Python interpreter accepts arbitrary commands in one of its parameters and execute them through the system's command line or console. If you’re still running an old and vulnerable version, you shouldn’t rely on the “trusted list” functionality as an invalid signature algorithm could still make a laced document appear as it comes from a trusted source.The attack relies on exploiting a directory traversal flaw, identified as CVE-2018-16858, to automatically execute a specific python library bundled within the software using a hidden onmouseover event. In the new dialog, you may select among four distinct levels of security, with High or Very High being the recommended options. LibreOffice settings menu to disable macros To set macro security on LibreOffice, go to Tools → Options → LibreOffice → Security, and click on ‘Macro Security’. If updating to the latest version is not possible for any reason, you can always opt to completely disable the macro features on your office suite, or avoid trusting any documents containing macros. If you’re using Linux and the aforementioned versions aren’t available on your distribution's package manager yet, you are advised to download the “deb”, or “rpm” package from the Download center or build LibreOffice from source. Since neither of these two applications offer auto-updating, you should do it manually by downloading the latest version from the respective download centers - LibreOffice, OpenOffice. For OpenOffice, that would be 4.1.10 and later, and for LibreOffice, 7.0.5 or 7.1.1 and later. If you’re using either of the open-source office suites, you’re advised to upgrade to the latest available version immediately. The same flaw impacts LibreOffice, which is a fork of OpenOffice spawned from the main project over a decade ago, and for their project is tracked as CVE-2021-25635. The discovery of the flaw, which is tracked as CVE-2021-41832 for OpenOffice, was the work of four researchers at the Ruhr University Bochum. "Allowing anyone to sign macro-ridden documents themselves, and make them appear as trustworthy, is an excellent way to trick users into running malicious code. The digital signatures used in document macros are meant to help the user verify that the document hasn’t been altered and can be trusted. LibreOffice and OpenOffice have pushed updates to address a vulnerability that makes it possible for an attacker to manipulate documents to appear as signed by a trusted source.Īlthough the severity of the flaw is classified as moderate, the implications could be dire. ![]()
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